PAF is degraded to inactive products by hydrolysis of the acetyl group at the sn-2 position to produce the biologically inactive products LYSO-PAF and acetate. This reaction is catalyzed by PAF acetylhydrolase.
NCBI Summary:
The protein encoded by this gene is a secreted enzyme that catalyzes the degradation of platelet-activating factor to biologically inactive products. Defects in this gene are a cause of platelet-activating factor acetylhydrolase deficiency. Two transcript variants encoding the same protein have been found for this gene.[provided by RefSeq, Dec 2009]
General function
Cell cycle regulation, Enzyme
Comment
Cellular localization
Secreted
Comment
candidate123
Ovarian function
Comment
Platelet-activating factor acetylhydrolase activity in human follicular fluid. Narahara H et al. Platelet-activating factor (PAF) has been implicated in a number of reproductive processes ranging from ovulation to parturition. To examine the role of PAF in the human periovulatory processes, the PAF-acetylhydrolase (PAF-AH) activity was assayed in the follicular fluid (FF) obtained in conjunction with the in vitro fertilization and embryo transfer (IVF-ET) procedure and the activity related to oocyte maturation. The PAF-AH activity was also related to the concentrations of estradiol (E2) and progesterone (P) in FF. PAF-AH activity was significantly lower in the FFs obtained from follicles of more than 20 mm in diameter. The enzyme activity was significantly lower in the FFs of patients with a successful outcome of their pregnancies. E2 concentrations were negatively correlated with PAF-AH activities in the FFs. No correlation was found between the PAF-AH activity and concentration of P in the FF. Significantly more mature oocytes were recovered in the group who subsequently become pregnant compared to the non-pregnant group. It is suggested that PAF may be increased following follicular maturation. The increase in PAF may contribute to oocyte maturation and to the successful outcome of pregnancy following fertilization. An additional function of the increased PAF in FF may also be the stimulation of the contraction of smooth muscle in the ovary, thereby assisting the extrusion of the oocyte cumulus cell mass and signaling the completion of ovulation.
Expression regulated by
Comment
Polycystic ovary syndrome (PCOS) affects 5% of reproductive aged women and is the leading cause of anovulatory infertility. A hallmark of PCOS is excessive theca cell androgen secretion, which is directly linked to the symptoms of PCOS. Our previous studies demonstrated that theca cells from PCOS ovaries maintained in long term culture persistently secrete significantly greater amounts of androgens than normal theca cells, suggesting an intrinsic abnormality. Furthermore, previous studies suggested that ovarian hyperandrogenemia is inherited as an autosomal dominant trait. However, the genes responsible for ovarian hyperandrogenemia of PCOS have not been identified. In this present study, Wood JR, et al carried out microarray analysis to define the gene networks involved in excess androgen synthesis by the PCOS theca cells in order to identify candidate PCOS genes. Analysis revealed that PCOS theca cells have a gene expression profile that is distinct from normal theca cells. Included in the cohort of genes with increased mRNA abundance in PCOS theca cells were aldehyde dehydrogenase 6 and retinol dehydrogenase 2, which play a role in all-trans-retinoic acid biosynthesis and the transcription factor GATA6. We demonstrated that retinoic acid and GATA6 increased the expression of 17alpha-hydroxylase, providing a functional link between altered gene expression and intrinsic abnormalities in PCOS theca cells. Thus, the analyses have 1) defined a stable molecular phenotype of PCOS theca cells, 2) suggested new mechanisms for excess androgen synthesis by PCOS theca cells, and 3) identified new candidate genes that may be involved in the genetic etiology of PCOS. This is one of the genes with Altered mRNA Abundance in PCOS Theca Cells as compared with normal theca cells Maintained Under Basal Conditions.
Ovarian localization
Theca, Follicular Fluid
Comment
Follicle stages
Comment
Phenotypes
PCO (polycystic ovarian syndrome)
Mutations
1 mutations
Species: human
Mutation name: None
type: naturally occurring fertility: subfertile Comment: Identification of the G994T polymorphism in exon 9 of plasma platelet-activating factor acetylhydrolase gene as a risk factor for polycystic ovary syndrome. Fan P et al. BACKGROUND Low-grade chronic inflammation and greater risks of cardiovascular diseases are often present in patients with polycystic ovary syndrome (PCOS). Platelet-activating factor (PAF) acetylhydrolase (PAF-AH) hydrolyzes and inactivates PAF and PAF-like oxidized phospholipids that are potent lipid mediators involved in inflammation and atherosclerosis. Deficiency of this enzyme is caused by a missense mutation (G994 --> T) in exon 9 of the plasma PAF-AH gene. The aim of the study was to investigate a possible association of this polymorphism with the risk of PCOS and to evaluate the effects of the genotype on the activity and distribution of PAFAH in Chinese patients. METHODS A total of 661 subjects (346 patients with PCOS and 315 healthy control women) from a population of Chinese Han nationality in Chengdu area were included in this study. PAFAH G994T genotype was studied using PCR and restriction fragment length polymorphism analysis. Total plasma PAF-AH, high-density lipoprotein (HDL)-associated PAF-AH (H-PAF-AH) and low-density lipoprotein (LDL)-associated PAF-AH (L-PAF-AH) activities were measured by the trichloroacetic acid precipitation procedure using [(3)H-acetyl] PAF and PAF C-16 as a substrate. RESULTS The prevalence of the mutant genotype (GT + TT) was significantly more frequent in patients with PCOS than in control subjects (12.7 versus 6.0%, P = 0.003). Genotype (GT + TT) remained a significant predictor for PCOS (P = 0.020) in prognostic models including age, body mass index, insulin resistance index, triglyceride, HDL and LDL as covariates. There was a significant difference in plasma PAF-AH, L-PAF-AH and H-PAF-AH activities between GG and GT genotypes in both the patient and control groups. The ratio of L-PAF-AH to H-PAF-AH activities was significantly higher after adjustment for multiple variables in patients with GT genotype compared with patients with GG genotype (P = 0.003). There were no significant differences in clinical, biochemical and metabolic parameters according to PAFAH G994T genotyping in patients with PCOS and control women. CONCLUSIONS The G994T polymorphism in PAFAH gene may be one of the genetic determinants for PCOS in Chinese Han women.