[Clinical effects of expanded frontal flap and flip scar flap in repairing partial nasal defect].

Objective: To investigate the clinical effects of expanded frontal flap and flip scar flap in repairing partial nasal defect. Methods: A retrospective observational study was conducted. From January 2012 to January 2022, 26 patients with partial nasal defects who met the inclusion criteria were admitted to the First Affiliated Hospital of Air Force Medical University, including 19 males and 7 females, aged 5 to 61 years. The surgery was performed in 4 stages. In the first stage, a rectangular skin and soft tissue expander (hereinafter referred to as expander) with suitable rated capacity was planted in frontal region and expanded by injecting water regularly. In the second stage, flip scar flap was grafted to reconstruct nasal inner lining, whose area was about 10% larger than the area of defect. The expanded frontal flap with pedicle was transferred to repair the nasal defect, whose pedicle was supraorbital vessel or supratrochlear vessel on the contralateral side of the defect, and the area of expanded flap was 20% larger than the nasal defect area after resection and flipping of scar flap. The donor site of expanded flap was sutured directly. After 3 weeks of flap transferring, the flap was delayed in the third stage. After 1 week of delaying operation, the pedicle of flap was cut off in the fourth stage. The number, rated capacity, injection volume, and expansion time of embedded expanders were recorded. The occurrences of complications including infection, hematoma, ulceration of expanded flap after the first stage operation, and blood supply disorder or necrosis of flap after operation in the second and fourth stages were observed. All the patients were followed up for 1 year at least, and the color of flap, scar of frontal donor site, symmetry of bilateral eyebrows, and the nasal appearance and ventilated function of external nasal tract were observed. Results: A total of 26 expanders were embedded in 26 patients. The rated capacity of expanders ranged from 100 to 300 mL. The injection volume was 1.0 to 1.5 times of the rated capacity of expanders. The expansion time ranged from 2.5 to 4.0 months, with an average time of 3 months. There were no complications occurred after each operation. The follow-up showed that the color of flap was similar to the normal nasal skin, the scar of frontal region was not obvious, the bilateral eyebrows were basically symmetrical, the nose had excellent appearance, ventilation function of external nasal tract was not affected, while some of the patients had downward rotation or unapparent tip-defining point of nose. Conclusions: Using the flip scar flap to reconstruct the nasal inner lining and pre-expanded frontal flap to reconstruct the nasal skin, without free cartilage transplantation to repair the partial nasal defects can achieve satisfied nasal appearance post operation, without abnormal external nasal ventilation function.

[Clinical effects of expanded forehead flaps in repairing midfacial defects].

Objective: To explore the clinical effects of expanded forehead flaps in repairing midfacial defects. Methods: From January 2003 to December 2018, 19 patients with midfacial defects were admitted to our unit, including 8 males and 11 females, aged 7 to 52 years. One cylindrical expander with rated capacity ranged from 100 to 170 mL was placed in the forehead of patients in the first stage of expansion, and the total water injection volume was about 2 times of the rated capacity of the expander during 1 to 2 months. The area of midfacial defects was 4 cm×2 cm to 9 cm×5 cm after resection in the second stage surgery. Expanded forehead flaps with vascular pedicle of supratrochlear vessels or frontal branch of superficial temporal vessels were used to repair the midfacial defects, with flap size ranging from 5 cm×2 cm to 16 cm×6 cm. The donor sites were closed by direct suturing. Three weeks later, the pedicle was divided. The complications, blood supply after flap transfer and pedicle division, and the treatment effects during follow-up were observed. Results: Among the patients, flaps of 11 patients had vascular pedicle of supratrochlear vessels; flaps of 8 patients had vascular pedicle of frontal branch of superficial temporal vessels. All the flaps survived with no complications and good blood supply after flap transfer and pedicle division. During the follow-up of 6 to 12 months after the third stage surgery of pedicle division of 12 patients, no lower eyelid ectropion occurred, the appearance of the flaps was similar to the surrounding tissue with no swelling. Conclusions: The application of expanded forehead flaps can not only repair the defects but also effectively avoid the complication of lower eyelid ectropion, which is a promising method in repairing midfacial defects.

Effect of OPCML gene on the biological behavior of gastric cancer cell line AGS.

The objective of this investigation was to explore the association of OPCML with gastric cancer and its clinical significance. The expression of OPCML was detected by immunohistochemistry in 118 cases of gastric carcinoma. The OPCML expression in the normal tissues and 7 kinds of gastric cells was assessed by RT-PCR. The recombinant plasmid pcDNA3.1-OPCML was constructed and transfected into AGS cells. CCK8 and colony formation assay were employed to analyze the effect of OPCML on AGS. Immunohistochemistry results showed that the expression of OPCML in gastric cancer was 68.6% and the expression of OPCML was negatively correlated with the depth of tumor invasion and tumor differentiation degree (P < 005); OPCML expression, depth of tumor invasion, lymph node metastasis and distant metastasis were important factors affecting the prognosis of the survival of the patients (P <0.05). OPCML m-RNA expression in the gastric cancer cells was significantly lower than that in the normal gastric mucosa. RT-PCR showed that the expression of OPCML was aberrantly increased in the cells transfected with pcDNA3.1-OPCML. CCK8 and colony formation assay showed that OPCML significantly inhibited the growth, proliferation, and colony formation of the AGS cells. OPCML plays an important role in gastric cancer, and may be a new prognostic indicator of gastric cancer.

Glutathione peroxidase-2 protects from allergen-induced airway inflammation in mice.

The aim of the present study was to identify and validate the biological significance of new genes/proteins involved in the development of allergic airway disease in a murine asthma model. Gene microarrays were used to identify genes with at least a two-fold increase in gene expression in lungs of two separate mouse strains with high and low allergic susceptibility. Validation of mRNA data was obtained by western blotting and immunohistochemistry, followed by functional analysis of one of the identified genes in mice with targeted disruption of specific gene expression. Expression of two antioxidant enzymes, glutathione peroxidase-2 (GPX2) and glutathione S-transferase omega (GSTO) 1-1 was increased in both mouse strains after induction of allergic airway disease and localised in lung epithelial cells. Mice with targeted disruption of the Gpx-2 gene showed significantly enhanced airway inflammation compared to sensitised and challenged wild-type mice. Our data indicate that genes encoding the antioxidants GPX2 and GSTO 1-1 are common inflammatory genes expressed upon induction of allergic airway inflammation, and independently of allergic susceptibility. Furthermore, we provide evidence to illustrate the importance of a single antioxidant enzyme, GPX2, in protection from allergen-induced disease.

Hyperresistance to cholesterol hydroperoxide-induced peroxidative injury and apoptotic death in a tumor cell line that overexpresses glutathione peroxidase isotype-4.

The selenoenzyme phospholipid hydroperoxide glutathione peroxidase (PHGPX; GPX4) plays a key role in eukaryotic defense against potentially lethal peroxidative injury and also regulation of physiological peroxide tone. In this work we focused on the cytoprotective antiperoxidant effects of GPX4, using a breast tumor epithelial cell line that over-expresses the enzyme. Wild-type COH-BR1 cells, which exhibit little (if any) GPX4 activity, were transfected with a construct encoding the mitochondrion-targeted long (L) form of the enzyme. Several transfectant clones were selected which expressed relatively large amounts of GPX4, as determined by both Northern and Western analysis. Enzyme activity ranged from 15-fold to 190-fold greater than that of wild-type or null-transfected cells. The functional ramifications of GPX4 overexpression were tested by challenging cells with photochemically generated cholesterol hydroperoxides (ChOOHs) in liposomal form. Compared with vector controls, overexpressing clones were found to be substantially more resistant to ChOOH-induced killing, as determined by annexin-V (early apoptotic) and thiazolyl blue (mitochondrial dehydrogenase) reactivity. Concomitantly, the clones exhibited a striking hyper-resistance to free radical-mediated lipid peroxidation, as assessed by labeling cell membranes with [(14)C]cholesterol and measuring a family of radiolabeled oxidation products (ChOX). L-form GPX4's antiperoxidant and cytoprotective effects could reflect its ability to detoxify ChOOHs as they enter cells and/or cell-derived lipid hydroperoxides arising from ChOOH one-electron turnover.

Mice with combined disruption of Gpx1 and Gpx2 genes have colitis.

Glutathione peroxidase (GPX)-1 and gastrointestinal (GI) epithelium-specific GPX (GPX-GI), encoded by Gpx1 and Gpx2, provide most GPX activity in GI epithelium. Although homozygous mice deficient in either the Gpx1 or Gpx2 gene appeared to be normal under standard housing conditions, homozygous mice deficient in both genes, double-knockout (KO) mice, had symptoms and pathology consistent with inflammatory bowel disease. These symptoms included a high incidence of perianal ulceration, growth retardation that started around weaning, and hypothermia that resembled that observed in calorie-restricted mice, even though the double-KO mice in our study were allowed to eat ad libitum. The growth retardation and hypothermia were components of cachexia, which is fatal in a high percentage of mice. Histological examination revealed that the double-KO mice had a high incidence of mucosal inflammation in the ileum and colon but not in the jejunum. Elevated levels of myeloperoxidase activity and lipid hydroperoxides were also detected in colon mucosa of these homozygous double-KO mice. These results suggest that GPX is essential for the prevention of the inflammatory response in intestinal mucosa.

Analysis of glutathione-related enzymes.

Glutathione peroxidase activity can be measured using a variety of substrates to define total glutathione peroxidase activity or the activity of subsets of the family of enzymes. The assays for these activities are spectrophotometric assays, and the specificity depends on the choice of substrate and/or prior treatment of the samples by chromatography or immunoprecipitation. This unit provides the assays and support protocols for synthesizing substrates and calculating specific activity.

Low glutathione peroxidase activity in Gpx1 knockout mice protects jejunum crypts from gamma-irradiation damage.

Gpx1 knockout (KO) mice had a higher number of regenerating crypts in the jejunum than did Gpx2-KO or wild-type mice analyzed 4 days after > or =10 Gy gamma-irradiation. Without gamma-irradiation, glutathione peroxidase (GPX) activity in the jejunal and ileal epithelium of Gpx1-KO mice was <10 and approximately 35%, respectively, of that of the wild-type mice. Four days after exposure to 11 Gy, GPX activity in wild-type and Gpx1-KO ileum was doubled and tripled, respectively. However, jejunal GPX activity was not changed. Thus the lack of GPX activity in the jejunum is associated with better regeneration of crypt epithelium after radiation. Gpx2 gene expression was solely responsible for the increase in GPX activity in the ileum, since radiation did not alter GPX activity in Gpx2-KO mice. The intestinal Gpx2 mRNA levels of Gpx1-KO and wild-type mice increased up to 14- and 7-fold after radiation, respectively. Although the Gpx1-KO jejunum had higher levels of PGE(2) than the wild-type jejunum after exposure to 0 or 15 Gy, these differences were not statistically significant. Thus whether GPX inhibits PG biosynthesis in vivo remains to be established. We can conclude that the Gpx2 gene compensates for the lack of Gpx1 gene expression in the ileal epithelium. This may have abolished the protective effect in Gpx1-KO mice against the radiation damage in the ileum.

Retinoic acid induces Gpx2 gene expression in MCF-7 human breast cancer cells.

We showed previously that the selenium-dependent glutathione peroxidase, GPX-GI, encoded by the Gpx2 gene, is highly expressed in the epithelium of the gastrointestinal (GI) tract and sporadically in breast tissue. To investigate whether Gpx2 gene expression is epithelium specific, we used in situ hybridization to show that Gpx2 mRNA is highly expressed in the crypt epithelium of human intestine. We also used Northern analysis to study human breast cells and found Gpx2 mRNA in human mammary epithelial cell lines as well as freshly isolated normal breast epithelial cells. Because we identified three putative retinoic acid response elements (RARE) in the Gpx2 gene, we examined the regulation of the Gpx2 gene expression by all-trans retinoic acid (RA) in RA-sensitive MCF-7 cells and RA-resistant HT29 cells. Without RA, MCF-7 cells had very low levels of Gpx2 mRNA and a low level of glutathione peroxidase (GPX) activity (17 mU/mg protein), whereas HT29 cells had a high level of Gpx2 mRNA and GPX activity (200 mU/mg protein). RA treatment increased Gpx2 mRNA level 3- to 11-fold and resulted in a fourfold increase of GPX activity (80 mU/mg protein) in MCF-7 cells. Neither Gpx2 mRNA level nor GPX activity was increased in HT29 cells. These results show that the Gpx2 gene is expressed in both breast and intestinal epithelium cells, and suggest that its expression can be highly regulated by retinoic acid, a known differentiation agent.

Glutathione peroxidase protects mice from viral-induced myocarditis.

Glutathione peroxidase 1 (GPX-1) is a selenium-dependent enzyme with antioxidant properties. Previous investigations determined that mice deficient in selenium developed myocarditis when infected with a benign strain of coxsackievirus B3 (CVB3/0). To determine whether this effect was mediated by GPX-1, mice with a disrupted Gpx1 gene (Gpx1-/-) were infected with CVB3/0. Gpx1-/- mice developed myocarditis after CVB3/0 infection, whereas infected wild-type mice (Gpx1+/+) were resistant. Sequencing of viruses recovered from Gpx1(-/-)-infected mice demonstrated seven nucleotide changes in the viral genome, of which three occurred at the G residue, the most easily oxidized base. No changes were found in virus isolated from Gpx1+/+ mice. These results demonstrate that GPX-1 provides protection against viral-induced damage in vivo due to mutations in the viral genome of a benign virus.

Selenium-dependent glutathione peroxidase-GI is a major glutathione peroxidase activity in the mucosal epithelium of rodent intestine.

Gpx2 mRNA, encoding a selenium-dependent glutathione peroxidase (GPX-GI), has been found to be highly expressed in the gastrointestinal tract (GI) mucosal epithelium. In this study, we show that GPX-GI is produced in the mucosal epithelium of the adult rat GI tract and that the activity levels are comparable to that from GPX-1. Post-mitochondrial supernatant GPX activity from the mucosal epithelium of the complete length of the small intestine was partially purified. A sample enriched for putative GPX-GI was fractionated by SDS-polyacrylamide gel electrophoresis. Polypeptides of 21 kDa and 22 kDa were digested with trypsin. After resolving the tryptic peptides by high pressure liquid chromatography (HPLC), the major peaks were analyzed for their amino acid sequence by Microflow-HPLC-Tandem Mass Spectrometry and automated Edman degradation sequencing. Both methods revealed that the 21-kDa sample contained rat GPX-GI determined by the sequence homology with the deduced mouse GPX-GI polypeptide sequence. Rat GPX-1 was also detected in the samples. AntiGPX-GI and antiGPX-1 antibodies were used to determine the distribution of the respective isoenzyme activities along the length of the intestine and with respect to the crypt to villus axis in rats. GPX-GI and GPX-1 activities were uniformly distributed in the middle and lower GI tract and with respect to the crypt to villus axis. GPX-GI activity accounted nearly the same percentage of the total GPX activity as GPX-1 in all of the these compartments. Studies on the distal ileum segment of wildtype and Gpx1 gene knockout mice showed that GPX-GI activity was also at parity with GPX-1 in the mucosal epithelium of this segment.

Expression and chromosomal mapping of mouse Gpx2 gene encoding the gastrointestinal form of glutathione peroxidase, GPX-GI.

GPX-GI is a cytosolic tetrameric Se-dependent glutathione peroxidase, similar in properties to GPX-1. Unlike the almost ubiquitous GPX-1, GPX-GI is mainly expressed in the epithelium of gastrointestinal tract. GPX-GI contributes to at least fifty percent of GPX activity in rodent small intestinal epithelium. The total GPX activity consists of at least 70% of selenium-dependent GPX activity in this compartment. By analyzing a panel of mouse interspecies DNA from the Jackson Laboratory's backcross resource, we mapped Gpx2 gene to mouse chromosome 12 between D12Mit4 and D12Mit5, near the Ccs1 locus which contains a colon cancer susceptibility gene. A pseudogene, Gpx2-ps is mapped to mouse chromosome 7. Comparison of Gpx2 gene expression in three pairs of C57BL/6Ha and ICR/Ha mice which are respectively resistant and sensitive to dimethylhydrazine-induced colon cancer, we found a higher Gpx2 mRNA level in C57BL/6Ha colon than ICR/Ha colon. Interestingly, a lower level of GPX activity is found in the resistant strain of mice. Because GPX-1 has three times higher specific activity than GPX-GI, our data suggest that the decreased GPX activity may result from a higher level of Gpx2 gene expression in those cells co-express Gpx1 gene.

The Gpx1 gene encodes mitochondrial glutathione peroxidase in the mouse liver.

Mitochondria have GPX and PHGPX activity. It has been an unsettled issue whether mitochondrial GPX is encoded by Gpx1. Unlike the Gpx4 gene which encodes PHGPX with alternative transcription and translation start sites determining the subcellular localization of PHGPX, the Gpx1 gene appears to have a single translation start site. Additionally, mitochondrial GPX has been shown to have different chromatographic and kinetic properties from the cytosolic GPX1. We studied mouse liver mitochondrial GPX activity in homozygous Gpx1-knockout mice. Mitochondria were enriched at the density of 1.10 g/ml in the Percoll gradients as shown by electron microscopy. The H2O2-reducing GPX activity in the highly enriched mitochondrial fraction of wild-type mouse liver is 2700 mU/mg which is about one-half of specific activity found in cytosol. There is less than 0.5% GPX activity in the cytosol and no GPX activity in the mitochondria of Gpx1-knockout mouse liver compared to the cytosol of wild-type mouse liver using H2O2 or cumene hydroperoxide as the substrate. The fact that the knockout mice express normal levels of plasma GPX as well as testis and liver PHGPX activity indicates that animals are not selenium-deficient. Based on these observations, we concluded that mitochondrial GPX is the product of the Gpx1 gene.

The mouse glutathione peroxidase Gpx2 gene maps to chromosome 12; its pseudogene Gpx2-ps maps to chromosome 7.

The GPX2 gene codes for GSHPx-GI, a glutathione peroxidase whose mRNA is readily detectable in the gastrointestinal tract. Although GPX2 is a single gene in humans, there are two genes in the mouse genome with homology to GPX2. By analyzing a panel of mouse interspecies DNA from the Jackson Laboratory's backcross resource, we have chromosomally mapped these two genes. One was mapped to the central region of mouse chromosome 12 between D12Mit4 and D12Mit5, near fos and Tgfb3. This region is homologous to human 14q24.1, where human GPX2 has been mapped, and most likely represents the functional mouse Gpx2 gene. The other Gpx2-like gene was mapped to mouse chromosome 7 between Pcsk3 and Hbb. We have isolated the latter gene from a P1 phage library. Its pseudogene nature is revealed by the sequence analysis: (a) it is intronless; (b) it has a single nucleotide deletion in the coding region; and (c) it has a poly(A) tail at its 3'-untranslated region.

Polymorphism and chromosomal localization of the GI-form of human glutathione peroxidase (GPX2) on 14q24.1 by in situ hybridization.

We have isolated a 3.3-kb DNA containing the two exons and a 2.6-kb intron of the human CPX2 gene. This gene encodes the intestinal isoenzyme of glutathione peroxidase, GSHPx-GI. Consistent signals were detected at 14q24.1 when this DNA was used as a probe for fluorescence in situ hybridization on metaphase chromosomes. Based on either single-stranded conformation polymorphism or sequencing analysis, two sites containing DNA polymorphism were found in the intron: the 5' end had a single A/T alteration, and the 3' end had a microsatellite of TC repeats.

The expression of an intestinal form of glutathione peroxidase (GSHPx-GI) in rat intestinal epithelium.

We have previously identified and characterized GSHPx-GI, which is a cellular selenium-dependent glutathione peroxidase (GSHPx) distinct from the classic GSHPx-1 and phospholipid hydroperoxide glutathione peroxidase (PHGPX). We have determined the level of GSHPx-GI mRNA expression in the rat gastrointestinal tract from esophagus to colon. Although GSHPx-GI mRNA is readily detectable throughout the GI tract, the highest level is detected in the ileum and cecum. We have also determined the levels of GSHPx-GI mRNA expression and several antioxidant enzyme activities along the villus-to-crypt axis in the rat small intestine by cell fractionation. GSHPx-GI mRNA is present at a similar level in all of the epithelial fractions, whereas GSHPx-1 mRNA is detectable only in the remnant. This suggests that GSHPx-GI is the major cellular tetrameric GSHPx expressed in intestinal epithelium, and the expression of GSHPx-GI in the GI tract is not likely regulated differentially through maturation of epithelial cells. In terms of enzymatic activity, although we detected lower glutathione S-transferase activity in the crypt epithelium, there was a marginal increase of PHGPX activity, a twofold increase of GSHPx activity, and a three- to fivefold increase of catalase activity in the crypt relative to the distal villus. Thus, the crypt epithelial cells may be better protected from peroxidative damage.

Expression of selenium-dependent glutathione peroxidase in human breast tumor cell lines.

In estrogen receptor (ER)-positive breast cancer cell lines, very low expression of glutathione peroxidase-1 (GPX-1) activity and hgpx1 mRNA has been observed. Such cell lines have been used as models in studies of resistance to redox cycling anticancer drugs. In particular, large increases in GPX-1 activity levels by expression of transfected GPX-1 cDNA have been shown to confer some resistance to such drugs. It has never been determined that such low GPX-1 expression is a common feature of breast cancer. Based on previous limited surveys of breast cancer cell lines, it has been suggested that there may be an inverse correlation between ER status and GPX-1 production. Here we report the results from a larger survey of breast cancer cell lines, including six recently isolated cell lines. A near absence of hgpx1 mRNA expression was observed in 3 of 13 ER-negative cell lines; 1 of 4 ER-positive cell lines had high production of GPX-1. Both observations weaken the proposed inverse correlation between ER status and GPX-1 production. We have evidence to suggest that one cell line, COH-BR-5 (ER-negative), lacked hgpx1 gene expression prior to culture. This is based on the finding of stable hgpx1 gene expression during serial culture of ER-negative breast cancer cell lines newly isolated from malignant effusion and absence of hgpx1 mRNA expression in COH-BR-5. Expression of hgpx2 mRNA (producing GPXGI, the GI tract GPX) was detected in several long and newly established, ER-negative breast cancer cell lines. Cell lines, COH-BR-5 and MDA-MB-175, expressed only hgpx2 mRNA. The hgpx2 mRNA was detected in COH-BR-5 and COH-BR-7 at low passage number, suggesting that hgpx2 gene expression occurs in breast cancer malignant effusion. Thus, studies of the role of GPX in redox drug resistance may account for changes in hgpx2 gene expression. Phospholipid hydroperoxide GPX activity was not found to be generally elevated above normal tissue levels in newly established breast cancer-derived cell lines.

Cloning and sequencing of the cDNA encoding a human testis phospholipid hydroperoxide glutathione peroxidase.

A human cDNA that encodes a polypeptide that has 94% deduced amino-acid sequence identity to porcine phospholipid hydroperoxide glutathione peroxidase was cloned from a testis library. The sequence shows preservation of the UGA selenocysteine codon, putative active-site Trp and Glu residues and a Tyr residue that is phosphorylated in the porcine protein. The 3'-UTR shows some conservation of sequences implicated in the insertion of selenocysteine at an opal codon in human glutathione peroxidase-1.

The human glutathione peroxidase genes GPX2, GPX3, and GPX4 map to chromosomes 14, 5, and 19, respectively.

cDNA probes of human glutathione peroxidase (GSHPx) genes, including the classic GPX1 (GSHPx-1), the newly characterized GPX2 (GSHPx-GI), the plasma enzyme GPX3 (GSHPx-P), and the phospholipid hydroperoxide glutathione peroxidase GPX4 (PHGPX), were hybridized to Southern blots containing genomic DNA from human x hamster somatic cell hybrids. GPX2 was mapped to chromosome 14, GPX3 to chromosome 5 and GPX4 to chromosome 19. Additionally, human chromosomes 3 and 21 and the X chromosome were shown to contain sequences homologous to GPX1, as reported previously.

Reactivity of plasma glutathione peroxidase with hydroperoxide substrates and glutathione.

We studied enzyme kinetics parameters of plasma glutathione peroxidase (GSHPx-P) and the major cellular enzyme, GSHPx-1, for the substrates, H2O2, linoleic acid hydroperoxide (LinOOH), and glutathione (GSH). The major objectives were to determine whether the relatively slow GSHPx-P enzyme had a lower reactivity with hydroperoxides or with GSH and to identify favored hydroperoxide substrates. The rate constants describing the reactivity of human GSHPx-P and human GSHPx-1 with LinOOH and H2O2 are in the same range; GSHPx-P is more reactive with LinOOH and GSHPx-1 is more reactive with H2O2. GSHPx-P also has a low level of reducing activity toward cholesterol 7 alpha-OOH and no detectable activity with the 5 alpha-OOH isomer in contrast to phospholipid hydroperoxide glutathione peroxidase (PHGPx) which readily reduced both isomers. GSHPx-P catalytic activity toward phospholipid hydroperoxides is demonstrable in the absence of detergents, enhanced at low concentrations by deoxycholate, and strongly inhibited by Triton X-100 and incorporation into liposomes. These properties are the opposite of PHGPx. These results suggest that GSHPx-P largely lacks the membrane interfacial properties of PHGPx. GSHPx-P exhibits a smaller GSH rate constant than GSHPx-1. This property partially explains the slower turnover of GSHPx-P with several hydroperoxide substrates; the low reactivity with GSH is not consistent with efficient GSHPx function in the bulk plasma volume. GSHPx-P kinetic properties suggest that it would function best as a free fatty acid hydroperoxidase in GSH-rich microenvironments. Minimally, the secretion of reduced enzyme would permit it to scavenge free fatty acid hydroperoxides.