Sequence of the E1 alpha subunit of branched-chain alpha-ketoacid dehydrogenase in two patients with thiamine-responsive maple syrup urine disease.

Some patients with maple syrup urine disease respond to thiamine administration with a reduction in ketoaciduria and increase in activity of branched-chain alpha-ketoacid dehydrogenase. The biochemical mechanism underlying this effect is unknown but may result from decreased affinity of the mutant enzyme for thiamine or from stabilization of the abnormal enzyme by thiamine. The E1 alpha subunit of the complex participates in the thiamine-dependent decarboxylation of branched-chain alpha-ketoacids. We sequenced the E1 alpha subunit by using reverse transcription of RNA followed by enzymatic amplification of cDNA in two patients with thiamine-responsive maple syrup urine disease. The deduced amino acid sequence of this subunit in the patients was identical to that in normal controls, suggesting that in the patients the thiamine-binding site is abnormal because of a mutation in the E1 beta subunit. Other possible explanations are (a) that a mutation in the E1 beta or E2 subunits either alters thiamine binding by E1 alpha because of allosteric interactions or causes the complex to be unstable and (b) that thiamine stabilizes the complex.

3-Hydroxy-3-methylglutaryl coenzyme A reductase activity in cultured fibroblasts from patients with mevalonate kinase deficiency: differential response to lipid supplied by fetal bovine serum in tissue culture medium.

3-Hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase activity was measured in extracts of cultured fibroblasts derived from patients with mevalonate kinase deficiency (MKD). For six patients studied, the mean activity of 63.3 +/- 41.1 pmol/min-mg protein (+/- 1 SD, range 37.7-146.2) was significantly higher than the mean value in three control fibroblast lines of 11.1 +/- 3.5 (+/- 1 SD, range 8.0-14.9). These values were obtained using cells subcultured in medium supplemented with 10% fetal bovine serum (FBS) 21 h prior to assay. When cells were deprived of cholesterol by subculturing for 21 h in delipidated FBS, the mean value for patient cells was increased to 230.8 +/- 78.5 pmol/min-mg protein (range 130.9-333.8) as compared to 109.5 +/- 47.1 (range 78.0-163.6) for controls. The activity of HMG-CoA synthase in extracts of fibroblasts derived from the patients was not elevated. The mevalonic acid concentration in the surrounding culture medium was assessed by stable isotope dilution assay. For five patients, the mean concentration in medium containing FBS was 0.92 +/- 0.37 microM (+/- 1 SD, range 0.46-1.48) in contrast to 1.24 +/- 0.83 microM (range 0.46-2.54) for cells subcultured in delipidated FBS. The mean value for three control fibroblast lines was 0.22 +/- 0.12 microM (+/- 1 SD, range 0.11-0.35) for cells subcultured in FBS as compared to 0.01 +/- 0.01 microM (range 0.0-0.01 microM) for cells sucultured in delipidated FBS.(ABSTRACT TRUNCATED AT 250 WORDS)

Mevalonate kinase in lysates of cultured human fibroblasts and lymphoblasts: kinetic properties, assay conditions, carrier detection and measurement of residual activity in a patient with mevalonic aciduria.

An assay has been developed for the measurement of mevalonate kinase activity in extracts of cultured human fibroblasts and lymphoblasts. Individual elements of the assay were investigated in order to achieve optimum conditions. Apparent Michaelis constants (KMapp) for the substrates mevalonic acid and adenosine-5'-triphosphate were 22 +/- 10 mumol/l and 0.42-0.53 mmol/l, respectively, in lysates of control fibroblast lines. The same values in lysates of a control lymphoblast line were 17 mumol/l and 0.23 mmol/l, respectively. Mevalonate kinase activity in extracts of cultured fibroblasts derived from 6 control individuals was 3.24 +/- (SD) 0.91 nmol/min/mg protein. The activity in extracts of fibroblasts derived from a patient with mevalonic aciduria was 0.15 +/- 0.10 nmol/min/mg protein, approximately 5% of the control mean. The parents and brother of the patient displayed mevalonate kinase activities in fibroblast extracts approximating 38-42% of the control mean. Substantially higher mevalonate kinase activity was documented in extracts of cultured lymphoblasts. When assayed on various occasions, the mean activity of mevalonate kinase in extracts of lymphoblasts derived from the parents, brother and maternal grandmother of the patient ranged from 27 to 32% of the mean activity of 9.8 +/- (SD) 3.4 nmol/min/mg protein measured in a parallel control lymphoblast line, while the mean activity in a maternal and paternal uncle approximated 65-89% of the same control mean. The mean activity in extracts of lymphoblasts derived from the patient approximated 2% of the control mean. The data suggest that the parents, brother and maternal grandmother are carriers of the defective gene responsible for mevalonate kinase deficiency, consistent with an autosomal recessive mode of inheritance.

Mevalonic aciduria--an inborn error of cholesterol and nonsterol isoprene biosynthesis.

A two-year-old boy presented with severe failure to thrive, developmental delay, anemia, hepatosplenomegaly, central cataracts, and dysmorphic features. Quantitative analyses of urinary organic acids revealed massive excretion of mevalonic acid, a metabolic precursor of cholesterol and nonsterol isoprenes: 46,000 to 56,200 mmol per mole of creatinine, as compared with 0.2 to 0.3 mmol per mole in normal children. The mevalonic acid concentration in plasma was also greatly increased at 440 mumol per liter (normal, less than 0.05). The activity of mevalonate kinase, the enzyme that catalyzes the first step in mevalonate metabolism, was severely deficient in the patient's fibroblasts, lymphocytes, and lymphoblasts. In the subsequent pregnancy of the patient's mother, gas chromatography-mass spectrometry demonstrated a marked elevation of mevalonic acid in the mother's urine and a 3000-fold elevation, as compared with control levels in the amniotic fluid, suggesting that the fetus was affected. The diagnosis was confirmed by demonstration of the deficiency of mevalonate kinase in amniocytes and ultimately in liver from the abortus. Intermediate activities of the enzyme in both parents indicated an autosomal recessive mode of inheritance. These observations identify an inherited disorder of cholesterol and nonsterol isoprene biosynthesis in humans.

Infectious and bleeding complications in patients with glycogenosis Ib.

Clinical, hematologic, and immunologic findings were reviewed in 21 patients with glycogenosis Ib. Fifteen of the patients suffered from moderate to severe bacterial infections. Ten patients had excessive epistaxis or bleeding from surgical sites, and eight suffered oral and anal mucosal ulceration. Sixteen of 21 patients exhibited chronic neutropenia associated with abnormalities in myeloid maturation and decreases in the bone marrow storage and peripheral marginating pools. Diminished neutrophil motility was documented in 14 of 15 patients tested, and adherence was decreased in three patients studied. Neutrophil microbicidal activity, reduction of nitroblue tetrazolium, and ingestion were normal in all patients tested. Bleeding times were prolonged in five of eight patients, and results of platelet function studies were abnormal in five individuals. Excessive bleeding in patients with glycogenoses Ia and Ib are similar and may be secondary to the functional deficiency of glucose-6-phosphatase. However, neutropenia, neutrophil dysfunction, and the resulting infectious complications are specific for Ib disease and may be related to abnormal glucose-6-phosphate transport.

Keratan and herparan sulfaturia: glucosamine-6-sulfate deficiency.

The pattern of excretion of urinary acid mucopolysaccharides (AMPS) has been helpful to establish the diagnosis of mucopolysaccharidoses. The importance of urine analysis for AMPS and the specific enzyme assays is exemplified in a 3 1/2 year old Caucasian male with severe mental retardation, small stature, thoracolumbar kyphosis, and dysostosis multiplex. Urine analysis for AMPS revealed excessive quantities of keratan and heparan sulfate. This mucopolysacchariduria was not associated with hepatosplenomegaly or corneal clouding. Enzymic studies on cultured skin fibroblasts indicated deficiency of N-acetylglucosamine-6-sulfate sulfatase. This enzyme deficiency is different from that responsible for Morquio's syndrome, and early recognition is essential for proper counseling.

Nonketotic hyperglycinemia: electroencephalographic and evoked potential abnormalities.

Five patients with nonketotic hyperglycinemia had serial EEGs and evoked-response studies. EEGs were grossly abnormal in all patients. In the neonatal period, the "suppression-burst" pattern was observed. The EEG changed to hypsarrhythmia during early or mid-infancy. In the second to fifth years of life, multifocal epileptiform discharges superimposed on diffuse slow background activity constituted the usual abnormality during wakefulness, but more severe disorganization of the EEG occurred in sleep with emergence of hypsarrhythmia. Four patients had abnormal brainstem auditory evoked responses, characterized by prolongation of I-V interval, and two had abnormal flash-induced visual evoked responses.

Carrier detection in Sanfilippo syndrome type B: report of six families.

Serum samples from 175 individuals in six Sanfilippo syndrome type B (SFB) families and 360 White controls were assayed for serum alpha-N-acetyl-D-glucosaminidase (NAG) activity. Only minimal overlap was observed between the controls' NAG activity distribution and that of the 12 obligate heterozygotes. The distribution of NAG activity was log transformed to reduce skewness, and segregation of family members with a prior risk of being a SFB carrier was well within expected limits. However, in one consanguineous family the NAG activity of both parents of one SFB obligate heterozygote was within the normal range for NAG activity. Plausible explanations for this finding are discussed. Additionally, the serum NAG activity of one control and her mother were found to lie within one standard deviation of the obligate heterozygote mean. These individuals are most probably carriers for SFB.

Endogenous glucose production in Type I glycogen storage disease.

The adaptive mechanisms that protect some patients with Type I glycogen storage disease from fasting hypoglycemia were examined in two young adults. Both maintained low normal fasting plasma glucose concentrations even during 3 day fasts; blood lactate concentrations increased during the first 12 hr and then decreased to normal during the second and third days. Acute hyperglycemic responses to glucagon nearly doubled after three days of starvation when compared with responses following 12 hr fasts. Enhanced glucagon-induced hyperglycemic changes also were observed following the administration of alcohol or glucocorticoids. However, fructose infusions failed to demonstrate hyperglycemic responses after a 3 day fast, alcohol or glucocorticoids. The present studies demonstrate endogenous glucose production in our patients despite an absence of the enzyme glucose-6-phosphatase. These findings could explain why some patients with Type I glycogen storage disease are protected from fasting hypoglycemia.

Kaufman syndrome (hydrometrocolpos, polydactyly, and congenital heart disease) with pituitary dysplasia, choanal atresia, and vertebral anomalies.

An infant was found to have the previously known manifestations of the Kaufman syndrome (hydrometrocolpos, postaxial polydactyly, and congenital heart disease) but also imperforate anus, malrotation of gut, congenital hip dislocation, and urogenital sinus. All of these anomalies have been separately reported in other cases of the syndrome. Three previously unreported problems present in this case were choanal atresia, pituitary dysplasia, and vertebral anomalies; these may well be component manifestations of the syndrome and not sporadic occurrences in our patient. Of particular clinical importance were the hypoglucocorticism and the hypoglucocorticism secondary to the pituitary dysplasia.

Linkage analysis using heterozygote detection in phenylketonuria.

This linkage investigation was undertaken utilizing an improved method for phenylketonuria (PKU) heterozygote detection. This method is based on studies of semi-fasting, noon-time, blood specimens obtained from 85 obligate heterozgotes and 45 controls who were neither pregnant nor on birth control medication. The best separation between heterozygotes and normals was achieved with a discriminant function involving the logarithms of the serum concentrations of phenylalanine, tyrosine and tryptophan. The theoretical overlap area between the distributions of heterozygotes and controls, based on the above function, was between the distributions of heterozygotes and controls, based on the above function, was 3.75%. In 19 obligate heterozygotes and 13 controls who were either pregnant or on birth control medication, the best separation was achieved with a discriminant function involving the logarithms of the serum concentrations of phenylalanine and tyrosine. The theoretical overlap area was 8.23%. These equations identified heterozygotes with sufficient accuracy to permit efficient genetic linkage analysis. We were unable to demonstrate genetic linkage between the PKU locus and 15 common blood, serum, and urinary markers. All but loose linkage (theta greater than 0.3) was excluded for Rh, ABO, Gc, Kidd, and AP. Moderate linkage exclusion (theta less than 0.2) was shown for PGM, Duffy, Hp, MNS, HL--A, and Kell. Close linkage (theta less than 0.1) was excluded for Amy2, 6PGD, P, and ADA. We were unable to find linkage heterogeneity between the Amish and non-Amish populations.

Structural comparison of hexosaminidases in primates.

1. beta-Hexosaminidase (hex) structure was compared in various primates, using thin-layer isoelectric focusing on polyacrylamide gels and quantitative microcomplement fixation. 2. Isoelectric focusing revealed no intraspecies differences and similar interspecies patterns. 3. Hex A and B are evolving at a moderate, but equal, rate and in a manner consistent with accepted phylogenetic patterns. 4. Quantitative microcomplement fixation revealed a closer homology between human hex A and chimpanzee A or human hex B and chimpanzee hex B than between human hex A and human hex B.

Phenylketonuria heterozygote detection in families with affected children.

Improved approaches to the problem of heterozygote detection for phenylketonuria (PKU) were developed in this study. The discrimination was based on 85 obligate heterozygotes and 45 controls who were neither pregnant nor on birth control medication. The best separation between hetrozygotes and normals was achieved with a linear discriminant function involving the logarithms of the serum concentrations of phenylalanine, tyrosine, and tryptophan. The theoretical overlap area between the distributions of heterozygotes and controls based on the above function, was 3.75%. In the 19 obligate hetrozygotes and 13 controls who were either pregnant or on birth control medication, the best separation was achieved with a linear discriminant function involving the logarithms of the serum concentrations of phenylalanine and tyrosine. The theoretical overlap area was 8.23%. The genetic accuracy of the discriminant function was confirmed by testing the results with parental-child exclusions, segregation analysis, and the frequency of heterozygosity in nonrelated collateral spouses. Finally, there was evidence suggesting that the antihypertensive agent, aldomet, alters serum tyrosine and tryptophan levels.

The Chicago variant of clinical galactosemia.

A new variant of clinical galactosemia with two hitherto unidentified alleles on the transferase locus in one family is described. This new clinical variant of transferase has 25% of normal control activity in blood and in skin fibroblasts, and the patient accumulates galactose-1-phosphate in blood on an unrestricted galactose diet. Using starch gel electrophoresis on the hemolysate of the family members, a fast-moving transferase with mobility in between those of the normal control and of the Duarte variant is identified. This new allele is designated as GALTC1 (fast-moving Chicago variant). In addition, a second new allele was documented in this family by studying the instability of the transferase enzyme in hemolysates of family members at 50 degrees C for various time intervals. This new allele is designated as GALTC2 (heat-labile Chicago variant). On the basis of these studies, the transferase genotype of this patient is thought to be a double heterozygote compound, GALTC1/GALTG.

Unusual association of Saethre-Chotzen syndrome and congenital adrenal hyperplasia.

This report describes and discusses the very rare occurrence of two heritable traits, the Saethre-Chotzen syndrome and congenital adrenal hyperplasia (21 hydroxylase deficiency, salt-losing type) in a female infant whose father presents the clinical manifestations of Saethre-Chotzen syndrome. Family study revealed no other instances of the recessively inherited adrenogenital syndrome. Other literature cases combining acrocephalosyndactyly and urogenital anomalies are discussed and compared.