人类胎盘羧酸酯酶在术语:酶的特性、分子克隆和多种形式存在的证据。
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燕B,杨Matoney L D
人类胎盘羧酸酯酶在术语:酶的特性、分子克隆和多种形式存在的证据。
胎盘。1999年9月,20 (7):599 - 607。
- PubMed ID
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10452915 (在PubMed]
- 文摘
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胎盘是一个临时的器官,是已知的代谢许多内源性和异型生物质化合物。羧酸酯酶代表一个家庭的酶水解各种酯类、酰胺、硫代酸酯。许多研究表明,羧酸酯酶广泛分布在哺乳动物组织,但对这些酶在胎盘。beplayapp本研究建立的动力学参数进行胎盘向几个p硝基酚和1-naphthol酯羧酸酯酶,并建立在胎盘这些酶的分子基础。摘要评述的酶水解率和羧基的p硝基酚酯作为底物浓度的函数(0.01 - -1.00 m m)是研究与人类胎盘微粒体混合从六个胎盘。这些研究数据产生一个线性Lineweaver-Burk情节与每个基质。为这些基质K (m)值范围从92到370 microm,和V (max)值范围从85到170 nmol /毫克/分钟。这些结果表明,每个基质由单一酶,水解或酶活动分不开,或者其中一个是主导。从所有单个微粒体胎盘含有酯酶活性对所有四种基质,并表现出一至三倍的变化。对p -nitrophenylacetate活动相关的活动对摘要评述(r (2) = 0.957)。 In contrast, the activity toward p -nitrophenylbutyrate correlated poorly with the activity toward 1-naphthylacetate (r(2)=0.121). These results suggest that placental microsomes have more than one carboxylesterase activity. Screening of a placental cDNA library with gene-trapping hybridization resulted in the isolation of three distinct cDNAs, designated PCE-1, PCE-2 and PCE-3. PCE-1 and PCE-2 have a significant sequence identity (approx 99 per cent) with liver carboxylesterases hCE and hCE-2, respectively. PCE-3 has a 96 per cent sequence identity with hCE but only at the first 874 nucleotide of the 5' end. The rest of the 1396 nucleotides of the 3' end exhibit no significant sequence identity with any known mammalian carboxylesterases. A probe derived from the 3' end of PCE-3 detected an approx 2.2 kb messenger transcript, the size of a regular carboxylesterase. However, the entire PCE-3 cDNA has multiple internal stop codons and encodes only 269 amino acids; half the size of a regular carboxylesterase. Northern blotting experiments detected the transcripts coding for PCE-1, PCE-2 or PCE-3 in all placentae, and the levels of these messengers showed an approx six-fold individual variation. Placenta 6 had the highest activity toward all four substrates, and highest levels of the messengers for PCE-1, PCE-2 and PCE-3. In contrast, placenta 1 had relatively high levels of messengers for PCE-1 and PCE-2, but the activity toward these four substrates was only moderate. These results suggest that a discrepancy between the messenger level and the enzyme protein exists or that there are other as yet unidentified carboxylesterase(s) in the placenta which contribute to the hydrolytic activity. Carboxylesterases are known to involve the detoxication and metabolic activation of various drugs, environmental toxicants and carcinogens. Therefore, placental carboxylesterases have both pharmacological and toxicological significance in the development of the fetus.