Population Normalization in SARS-CoV-2 Wastewater-Based Epidemiology: Implications from Statewide Wastewater Monitoring in Missouri

O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=81 SRC="FIGDIR/small/22279459v1_ufig1.gif" ALT="Figure 1"> View larger version (24K): org.highwire.dtl.DTLVardef@debf50org.highwire.dtl.DTLVardef@1e21da2org.highwire.dtl.DTLVardef@78708org.highwire.dtl.DTLVardef@3239ee_HPS_FORMAT_FIGEXP M_FIG C_FIG The primary objective of this study was to identify a universal wastewater biomarker for population normalization for SARS-CoV-2 wastewater-based epidemiology (WBE). A total of 2,624 wastewater samples (41 weeks) were collected weekly during May 2021-April 2022 from 64 wastewater facilities across Missouri, U.S. Three wastewater biomarkers, caffeine and its metabolite, paraxanthine, and pepper mild mottle virus (PMMoV), were compared for the population normalization effectiveness for wastewater SARS-CoV-2 surveillance. Paraxanthine had the lowest temporal variation and strongest relationship between population compared to caffeine and PMMoV. This result was confirmed by data from ten different Wisconsins WWTPs with gradients in population sizes, indicating paraxanthine is a promising biomarker of the real-time population across a large geographical region. The estimated real-time population was directly compared against the population patterns with human movement mobility data. Of the three biomarkers, population normalization by paraxanthine significantly strengthened the relationship between wastewater SARS-CoV-2 viral load and COVID-19 incidence rate the most (40 out of 61 sewersheds). Caffeine could be a promising population biomarker for regions where no significant exogenous caffeine sources (e.g., discharges from food industries) exist. In contrast, PMMoV showed the highest variability over time, and therefore reduced the strength of the relationship between sewage SARS-CoV-2 viral load and the COVID-19 incidence rate, as compared to wastewater data without population normalization and the population normalized by either recent Census population or the population estimated based on the number of residential connections and average household size for that municipality from the Census. Overall, the findings of this long-term surveillance study concluded that the paraxanthine has the best performance as a biomarker for population normalization for SARS-CoV-2 wastewater-based epidemiology.

Myocardial infarction after epilepsy onset: A population-based retrospective cohort study.

INTRODUCTION: Cardiovascular comorbidities of epilepsy such as hypertension, hyperlipidemia, and diabetes are associated with myocardial infarction (MI). Little data on the development of subsequent cardiovascular disease (CVD) in persons with epilepsy (PWE) are available, with inconsistent findings regarding the association between epilepsy and subsequent MI. A higher risk of MI among adults (without prior MI) following epilepsy diagnosis compared with that among controls was hypothesized. METHODS: This retrospective cohort study used statewide hospital and emergency department (ED) encounter data from 2000-2013 for South Carolina residents aged >18 years without prior MI at the onset of epilepsy, or the first encounter for controls. Persons with epilepsy were compared with 1) persons with migraine (PWM), whose neurological condition has characteristics similar to epilepsy; and 2) persons with isolated lower extremity fracture (PWLF). Subsequent MI was defined as a diagnosis of MI after the first clinical encounter for epilepsy, migraine, or lower extremity fracture (LEF); the association was evaluated with Cox proportional hazard modeling methods. RESULTS: In this study, 2.2% of PWE, 0.6% of PWM, and 1.2% of PWLF had a subsequent MI. Persons with epilepsy were significantly more likely to be non-Hispanic Black (NHB), be covered by Medicaid, and reside in a rural or low income area compared with PWM and PWLF. Specific cardiovascular disease risk factors were more prevalent in PWE than in PWM and PWLF. After adjustment, the hazard of subsequent MI in PWE was 48% higher than in PWM (hazard ratio (HR) = 1.48; 95% confidence intervals (CI) = 1.31-1.67) and 24% higher than in PWLF (HR = 1.24; 95% CI = 1.10-1.39). The hazard of MI increased with increasing age and number of additional comorbidities and was higher in males, those living in rural areas, and those with specific cardiovascular risk factors. CONCLUSION: Persons with epilepsy had moderately elevated risk of subsequent MI compared with PWM or PWLF. The association between epilepsy and MI needs to be further investigated, and clinical care of PWE should include evaluation and management of risk factors for MI.

Mortality following status epilepticus in persons with and without epilepsy.

PURPOSE: Incidence of status epilepticus (SE) ranges from 6.8 to 41.0 per 100,000 population. Although SE is associated with significant morbidity and mortality, the temporal relationship between SE, epilepsy, and mortality is less clear. The risk of all-cause mortality following SE with and without prior epilepsy was investigated. METHOD: This study identified hospitalizations and emergency department visits for persons with SE and persons with epilepsy between 2000 and 2013. Excluded were those with epilepsy subsequent to SE, epilepsia partialis continua, less than 90days follow-up, and less than 2 years of data prior to first diagnosis. The cohort was grouped into: 1) SE only, 2) post-epilepsy SE (PES), and 3) epilepsy only. The risk of mortality was estimated using Cox proportional hazard models adjusting for potential confounders. RESULTS: The cohort (N=82,331) consisted of 1296 SE only cases (1.6%); 2136 PES cases (2.6%); and 78,899 epilepsy only controls (95.8%) with 24.9%, 29.2% and 20.0% mortality, respectively. Compared with controls, the hazard of mortality was increased for those with SE only (hazard ratio [HR]=1.61, 95% CI=1.41-1.82) and PES (HR=1.16, 95% CI=1.07-1.25) after adjustment for demographic and clinical factors. Prior stroke, central nervous system infection, and brain tumor increased the mortality hazard. CONCLUSION: There is a statistically significant increased risk of all-cause mortality with SE. The risk is stronger in those with no prior epilepsy. Specific etiologies increase mortality risk in those with SE warranting further investigation of the complex associations between these etiologies and SE.

Mortality in people with epilepsy: A statewide retrospective cohort study.

RATIONALE: People with epilepsy (PWE) have a higher risk of mortality than the general population, because of disparities in the receipt of appropriate epilepsy care, which may be affected by socioeconomic status, race/ethnicity and insurance coverage. Increased epilepsy prevalence has been associated with black race, low educational attainment, unemployment, and low income levels. Rural/urban residence may affect health through individual or environmental factors. Health disparities seen in rural residents are likely amplified in rural PWE because of limited access to specialized care. This analysis aims to examine the risk of mortality attributable to rural residence in the statewide population of South Carolina (SC) after adjusting for potential confounders. METHODS: This statewide retrospective cohort study of PWE seen in SC non-federal hospitals and emergency departments from 2000 to 2013 describes the hazard of mortality by rural/urban residential status in addition to other demographic and clinical characteristics. Differences in proportions were assessed by comparison of 95% confidence intervals. The association of rural/urban residence with mortality was further evaluated with Cox proportional hazard regression controlling for demographic and clinical covariables. RESULTS: 62,794 PWE were identified, of whom 21,451 (25.7%) had died. Deceased PWE were more likely to be rural residents, black, older than age 45, Medicare insured, in the middle income group, and have 5 or more comorbid conditions compared with living PWE. After adjustment for all other covariables, the risk of mortality did not differ by rural/urban residence. Blacks had a weak but significantly higher risk than whites (hazard ratio (HR)=1.14; 95% confidence interval (CI)=1.11, 1.18) while PWE of other races had a slightly lower risk of mortality (HR=0.79; 95% CI=0.67, 0.93). Male PWE had higher hazard as did Medicare, Medicaid or commercially insured PWE, those living in zip codes with annual median incomes less than $36,000, and those with 2 or more comorbid conditions. CONCLUSIONS: While other covariables were more strongly associated with mortality after adjustment (older age, insurance coverage, income level of zip code, and number of comorbidities), the finding of a higher hazard in black PWE than white PWE after adjustment for rural/urban residence and other demographic and clinical covariables is a concern. Further, the increased risk of mortality with higher numbers of comorbid conditions warrants regular management of these conditions.

Population-based comparative analysis of risk of death in children and adolescents with epilepsy and migraine.

OBJECTIVE: Follow-up studies of children and adolescents with epilepsy (CAW-E) have revealed higher risk of mortality than children in the general population. The mortality experience of CAW-E relative to patients with other common neurologic disorders in the pediatric age group is yet undetermined. The objectives of this study are the following: (1) to compare the causes and the adjusted risk of death in CAW-E with that of children and adolescents with migraine (CAW-M) in reference to children and adolescents with lower extremity fracture (CAW-LEF), and children and adolescents in the general population; (2) to evaluate if disparate mortality risks exist by demographic characteristics. METHODS: This retrospective cohort study included 56,781 children and adolescents 0-18 years of age hospitalized or treated in an emergency or outpatient department from 2000 to 2011 for epilepsy, migraine, or lower extremity fracture from all nonfederal health care facilities. Data on deaths were acquired from linked multiple causes of death data file using person-specific unique identifiers. Time of follow-up was from initial clinical encounter to time of death or censoring date of December 31, 2011. The association of risk characteristics with mortality was examined with Cox proportional hazard model after adjusting for potential confounders. RESULTS: Four hundred forty-seven CAW-E and 125 CAW-M died yielding mortality rates of 8.71 and 1.36 per 1,000 person-years, respectively. The 5-year risk of death was 4.38% for CAW-E, 0.68% for CAW-M, and 0.71% for CAW-LEF. Adjusted hazard ratios (HRs) were 3.81 (95% confidence interval [CI] 3.08-3.72) in CAW-E and 1.14 (95% CI 0.94-1.34) in CAW-M relative to CAW-LEF. Risk of death from neurodevelopmental comorbidities was 5.86 (95% CI 4.24-8.08) times greater than those without in the model that compared epilepsy with LEF. SIGNIFICANCE: There is an elevated risk of death in CAW-E with neurodevelopmental comorbidities that remains to be proven.

Stroke after adult-onset epilepsy: a population-based retrospective cohort study.

BACKGROUND: Earlier studies indicate a higher risk of subsequent stroke in PWE aged ≥60. However, little is known of the incidence of subsequent stroke in people with epilepsy (PWE) aged 35 through 60. We determined the risk factors that increase the incidence of stroke following adult-onset epilepsy in a large statewide population over a 10-year period. METHODS: South Carolina hospital discharge and emergency department (ED) data from 2000 to 2011 were used. The study was limited to persons aged ≥35years without prior stroke. Cases included patients diagnosed with epilepsy who were hospitalized or visited the ED. Controls were people with an isolated fracture of the lower extremity without any history of epilepsy or seizure disorders, presumed to approximate the health status of the general population. Epilepsy, fracture, stroke, and comorbid conditions were ascertained by diagnostic codes from health-care encounters. Only persons having stroke occurring ≥6months after the onset of epilepsy or after the first clinical encounter for controls were included. Cox proportional hazards modeling was performed to determine the risk of stroke. RESULTS: There were 21,035 cases with epilepsy and 16,638 controls who met the inclusion criteria. Stroke incidence was 2.5 times higher following adult-onset epilepsy (6.3%) compared with controls (2.5%). After adjusting for comorbidities and other factors, cases with epilepsy showed a 60% higher risk of stroke (HR=1.6; 95% CI: 1.42-1.80) compared with controls. Nearly half of the strokes in cases with epilepsy occurred in those with first diagnosis between ages 35 and 55. Somatic comorbidities associated with increased risk of stroke were more prevalent in cases with epilepsy than controls yet similar in both groups with stroke. Risk of stroke increased with increasing age in both groups. However, the risk of stroke in cases with epilepsy increased faster and was similar to that in controls who were ≥10years older. CONCLUSION: Adult-onset epilepsy at age 35 and older warrants consideration for occult cerebrovascular disease as an etiology of the epilepsy, which may also increase the risk of subsequent stroke. Somatic comorbidities frequently associated with epilepsy include comorbid conditions that share the same underlying pathology with stroke (i.e., hypertension, hyperlipidemia, myocardial infarction, diabetes, and arteriosclerosis). This increased risk of stroke in patients with adult-onset epilepsy should dictate the evaluation and management of stroke risk factors to prevent stroke.

Epilepsy beyond seizure: a population-based study of comorbidities.

Comorbid conditions may affect the quality of life in persons with epilepsy (PWE) more than seizures. Using legally mandated healthcare encounter data, somatic, psychiatric, and neurodevelopmental comorbidities in a large population-based cohort of PWE, were compared to persons with migraine (PWM), a similar neurologic condition, and lower extremity fracture (PWLF), otherwise healthy controls. 64,188 PWE, 121,990 PWM, and 89,808 PWLF were identified from inpatient, outpatient, and emergency department from 2000 to 2011. Epilepsy was ascertained with ICD-9-CM code 345; migraine with 346; fracture of the tibia, fibula, and ankle with 823 and 824. Common comorbidities of epilepsy were identified from the literature. Differences in prevalence among PWE, PWM, and PWLF were assessed by comparison of 95% confidence intervals (CI) constructed under the assumption of independence and normal approximation. The association of the comorbid conditions with epilepsy and migraine, compared to lower extremity fracture, were evaluated with polytomous logistic regression controlling for demographic and mortality covariables. PWE had significantly elevated prevalence of comorbidities compared with PWM and PWLF. Compared with PWLF, the adjusted odds ratios (OR) of having both somatic and psychiatric/neurodevelopmental comorbidities were 5.44 (95% CI=5.25-5.63) and 2.49 (95% CI=2.42-2.55) in PWE and PWM, respectively. The association with epilepsy was the strongest for cognitive dysfunction (OR=28.1; 95% CI=23.3-33.8); autism spectrum disorders (OR=22.2; 95% CI=16.8-29.3); intellectual disability (OR=12.9; 95% CI=11.6-14.3); and stroke (OR=4.2; 95% CI=4.1-4.4). The absolute risk increase in PWE compared with PWM for any somatic or psychiatric/neurodevelopmental comorbidity was 58.8% and 94.3%, respectively. Identifying comorbidities that are strongly and consistently associated with seizures, particularly disorders with shared underlying pathophysiology, is critical in identifying specific research and practice goals that may ultimately improve the quality of life for PWE. This study contributes to that effort by providing population-based comorbidity data for PWE compared with PWM and PWLF.

A population-based study of risk of epilepsy after hospitalization for traumatic brain injury.

PURPOSE: This study was undertaken to determine the risk of developing posttraumatic epilepsy (PTE) within 3 years after discharge among a population-based sample of older adolescents and adults hospitalized with traumatic brain injury (TBI) in South Carolina. It also identifies characteristics related to development of PTE within this population. METHODS: A stratified random sample of persons aged 15 and older with TBI was selected from the South Carolina nonfederal hospital discharge dataset for four consecutive years. Medical records of recruits were reviewed, and they participated in up to three yearly follow-up telephone interviews. RESULTS: The cumulative incidence of PTE in the first 3 years after discharge, after adjusting for loss to follow-up, was 4.4 per 100 persons over 3 years for hospitalized mild TBI, 7.6 for moderate, and 13.6 for severe. Those with severe TBI, posttraumatic seizures prior to discharge, and a history of depression were most at risk for PTE. This higher risk group also included persons with three or more chronic medical conditions at discharge. DISCUSSION: These results raise the possibility that although some of the characteristics related to development of PTE are nonmodifiable, other factors, such as depression, might be altered with intervention. Further research into factors associated with developing PTE could lead to risk-reducing treatments.

Psychosocial factors associated with stigma in adults with epilepsy.

Living Well with Epilepsy II called for further attention to stigma and its impact on people with epilepsy. In response, the South Carolina Health Outcomes Project on Epilepsy (SC HOPE) is examining the relationship between socioeconomic status, epilepsy severity, health care utilization, and quality of life in persons diagnosed with epilepsy. The current analysis quantifies perceived stigma reported by adults with epilepsy in relation to demographic, seizure-related, health, and psychosocial factors. It was found that reported levels of stigma were associated with interactions of seizure worry and employment status, self-efficacy and social support, and quality care and age at seizure onset. This information may be used to target and develop evidence-based interventions for adults with epilepsy at high risk for perceived stigma, as well as to inform epilepsy research in self-management.

Caregiver perceptions of seizure severity in pediatric epilepsy.

PURPOSE: Seizure severity has been investigated using multiple tools over the years, and its defining features continue to be debated. Severity ratings are necessary for medical, psychological, and epidemiologic investigations. Adults with epilepsy have been evaluated more than youth with epilepsy. METHODS: Seizure severity was evaluated as part of a larger study that included youth and caregiver self-report measures of the emotional and social variables that occur in epilepsy. RESULTS: The results indicate that a longer recovery time from the last seizure and a longer duration of seizure influence how severe a caregiver judges seizures. The usual elements such as type of epilepsy, frequency of seizures, and most recent seizure were not significantly related to severity rating. Behavior ratings were also not related to severity rating. DISCUSSION: Clinicians often rely heavily on caregiver information during clinic visits to help inform treatment decisions; therefore, a standard measure of seizure severity from the caregivers' perception has clinical utility. Rather than assuming what makes a seizure severe to a parent, more research should be conducted on what elements contribute to severity, as judged by both the parent and youth.

Prevalence of self-reported epilepsy, health care access, and health behaviors among adults in South Carolina.

Behavioral Risk Factor Surveillance System data from South Carolina for 2003-2005 were used to determine epilepsy prevalence and prevalence variation by demographic subgroups, and to compare health insurance coverage, health care visits, and health-related behaviors among persons with epilepsy and the general population. Two percent of respondents reported they had ever been told by a doctor that they had epilepsy, and 1% reported active epilepsy. Almost half of those with active epilepsy reported a seizure in the prior 3 months. More than one-third of respondents with active epilepsy reported that there was a time in the past 12 months when they needed to see a doctor but could not because of cost. Persons with epilepsy were more likely to smoke and have less physical activity. Persons with epilepsy need better access to health care, as well as interventions focused on smoking cessation and increased physical activity.

Allosteric dominance in carbamoyl phosphate synthetase.

A linked-function analysis of the allosteric responsiveness of carbamoyl phosphate synthetase (CPS) from E. coli was performed by following the ATP synthesis reaction at low carbamoyl phosphate concentration. All three allosteric ligands, ornithine, UMP, and IMP, act by modifying the affinity of CPS for the substrate MgADP. Individually ornithine strongly promotes, and UMP strongly antagonizes, the binding of MgADP. IMP causes only a slight inhibition at 25 degreesC. When both ornithine and UMP were varied, models which presume a mutually exclusive binding relationship between these ligands do not fit the data as well as does one which allows both ligands (and substrate) to bind simultaneously. The same result was obtained with ornithine and IMP. By contrast, the actions of UMP and IMP together must be explained with a competitive model, consistent with previous reports that UMP and IMP bind to the same site. When ornithine is bound to the enzyme, its activation dominates the effects when either UMP or IMP is also bound. The relationship of this observation to the structure of CPS is discussed.

Allosteric effects of carbamoyl phosphate synthetase from Escherichia coli are entropy-driven.

When catalyzing the formation of MgATP and carbamate from MgADP and carbamoyl phosphate, Escherichia coli carbamoyl phosphate synthetase (CPS) binds MgADP with a large negative change in heat capacity. The magnitude of this heat capacity change is not appreciably altered by the presence of a saturating concentration of either the allosteric activator ornithine or the inhibitor UMP despite the substantial and opposing effects these ligands have on the binding affinity for MgADP. By contrast, no detectable change in heat capacity is associated with the thermodynamic coupling between MgADP and either ornithine or UMP. The sign of the apparently constant enthalpic and entropic contributions to the coupling free energy for each of these ligands is opposite that of the coupling free energy, indicating that the observed allosteric phenomenology is in net opposed by the enthalpy of the interaction and instead arises from a change in entropy of the system. IMP produces only a very small allosteric effect as indicated by a near-zero value for the MgADP-IMP coupling free energy. However, the enthalpic and entropic contributions are individually larger in absolute value for the IMP coupling than for those pertaining to the other allosteric ligands, and entropy dominates the coupling free energy above 36 degrees C, causing IMP to become an activator at high temperature. In addition, the sign of the coupling enthalpy and entropy for IMP has the same sign as the coupling enthalpy and entropy produced by ornithine, suggesting that IMP and ornithine may similarly influence the enzyme at a molecular level despite binding to different allosteric sites on the enzyme. The data are consistent with a model in which the actions of the allosteric ligands arise primarily from changes in the conformational degeneracy introduced by each ligand. With this model, one can also rationalize the failure of these allosteric ligands to substantially influence kcat.

Measurement of glass transition temperatures in freeze concentrated solutions of non-electrolytes by electrical thermal analysis.

The electrical resistance (R) of frozen aqueous solutions was measured as a function of temperature in order to determine whether this technique can be applied for determination of glass transition temperatures of maximally freeze concentrated solutions (Tg') of non-electrolytes which do not crystallize during freezing. Electrical thermal analysis (ETA) thermograms of frozen solutions containing the solute alone show a gradual change in slope over the temperature range of interest, with no inflection point which corresponds to Tg'. However, addition of low levels (about 0.1%) of electrolyte changes the shape of the thermogram into a biexponential function where the intersection of the two linear portions of the log (R) vs. T plot corresponds to the glass transition region. The total change in log (R) over the temperature range studied increases as the ionic radius of the reporter ion increases. The sharpest inflection points in the log (R) vs T curves, and the best correlation with DSC results, were obtained with ammonium salts. Tg' values measured by ETA were compared with values measured by DSC. DSC thermograms of solutes with and without electrolyte (0.1%) show that the electrolyte decreases Tg' by about 0.5 to 1.0 degrees C. However, Tg' values measured by ETA are somewhat higher than those measured by DSC, and difference between the two methods seems to increase as Tg' decreases. Tg' as measured by ETA is less heating rate dependent than DSC analysis, and ETA is a more sensitive method than DSC at low solute concentrations and at low heating rates.(ABSTRACT TRUNCATED AT 250 WORDS)

Secondary 18O and primary 13C isotope effects as a probe of transition-state structure for enzymatic decarboxylation of oxalacetate.

A new method for directly measuring 18O isotope effects on decarboxylation reactions has been developed. By running the reaction under high vacuum (10(-5) torr), CO2 leaves the solution before exchange with the oxygens of water to an extent greater than 2%. Thus, the method permits determination of 18O isotope effects with the precision of the isotope ratio mass spectrometer, and without the necessity of resorting to the remote label method and its attendant required syntheses. The method is used to determine 18O isotope effects for decarboxylation of oxalacetate (OAA) by Mg2+, and enzymatically by OAA decarboxylase from Pseudomonas putida; 13C isotope effects are also reported for this enzyme, as well as for decarboxylation of OAA by pyruvate kinase. Initial velocity patterns and pH profiles are reported for the P. putida enzyme, and all available data are used to discuss the kinetic and chemical mechanism of decarboxylation.

Temperature-induced inversion of allosteric phenomena.

Two instances, involving the enzymes carbamoyl-phosphate synthetase from Escherichia coli and phosphofructokinase from Bacillus stearothermophilus, respectively, are described in which increasing temperature alone causes the actions of an allosteric ligand to change from inhibition to activation. In neither case are these effects due to a change in the activation energy of the enzyme catalyzed reaction induced by the allosteric ligand. Rather, they are due to temperature-dependent changes in the extent to which the binding of allosteric ligand modifies the affinity of the enzyme for substrate. The data can be readily explained by an analysis of the apparent delta H and delta S components of the coupling free energy, which quantitatively describe the actions of allosteric ligands that act in this manner. These observations underscore the shortcomings of expecting to explain the actions of an allosteric ligand solely by the structural perturbations that accompany the binding of an allosteric ligand such as those often revealed by x-ray crystallography.

Quantifying the allosteric properties of Escherichia coli carbamyl phosphate synthetase: determination of thermodynamic linked-function parameters in an ordered kinetic mechanism.

The effects of the allosteric ligands UMP, IMP, and ornithine on the partial reactions catalyzed by Escherichia coli carbamyl phosphate synthetase have been examined. Both of these reactions, a HCO3(-)-dependent ATP synthesis reaction and a carbamyl phosphate-dependent ATP synthesis reaction, follow bimolecular ordered sequential kinetic mechanisms. In the ATPase reaction, MgATP binds before HCO3- as established previously for the overall reaction catalyzed by carbamyl phosphate synthetase [Raushel, F. M., Anderson, P. M., & Villafranca, J. J. (1978) Biochemistry 17, 5587-5591]. The initial velocity kinetics for the ATP synthesis reaction indicate that MgADP binds before carbamyl phosphate in an equilibrium ordered mechanism except in the presence of ornithine. Determination of true thermodynamic linked-function parameters describing the impact of allosteric ligands on the binding interactions of the first substrate to bind in an ordered mechanism requires experiments to be performed in which both substrates are varied even if only one is apparently affected by the allosteric ligands. In so doing, we have found that IMP has little effect on the overall reaction of either of these two partial reactions. UMP and ornithine, which have a pronounced effect on the apparent Km for MgATP in the overall reaction, both substantially change the thermodynamic dissociation constant for MgADP from the binary E-MgADP complex, Kia, in the ATP synthesis reaction, with UMP increasing Kia 15-fold and ornithine decreasing Kia by 18-fold. By contrast, only UMP substantially affects the Kia for MgATP in the ATPase reaction, increasing it by 5-fold.(ABSTRACT TRUNCATED AT 250 WORDS)