人血小板中的一种肽酶，能脱除速激肽。可能是溶酶体“保护蛋白”。
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Jackman HL, Tan FL, Tamei H, Beurling-Harbury C, Li XY, Skidgel RA, Erdos EG
人血小板中的一种肽酶，能脱除速激肽。可能是溶酶体“保护蛋白”。
生物化学杂志1990年7月5日;265(19):11265-72。
- PubMed ID
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1694176 (查看PubMed］
- 摘要
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我们在人类血小板中发现了一种酶，可以脱酰胺P物质和其他速激肽。由于氨基化的羧基末端对生物活性很重要，我们对该脱酰胺酶进行了纯化和表征。该酶由凝血酶从人血小板中释放，通过硫酸铵沉淀纯化至均匀，然后在辛基- sepharose柱上层析，并聚焦于PBE 94。纯化的酶具有酯酶、肽酶和脱酰胺酶活性。肽酶(糠酰丙烯酰- phee - phe)在pH 5.0时活性最佳，而酯酶(苯甲酰-酪氨酸乙酯)和脱酰胺酶(d - ala2 - leu5 -脑啡酰胺)在pH 7.0时活性最佳。对于生物学上重要的肽，该酶在中性状态下作为脱酰胺酶(物质P，神经激肽a和eledoisin)和羧基肽酶(缓激肽，血管紧张素I，无物质P的酸，无催产素的酸)，尽管羧基肽酶在pH值5.5时作用更快。脑啡肽在脑啡胺脱酰胺过程中释放，不发生裂解。催产素的Gly9-NH2释放不脱酰胺。具有倒数第二个精氨酸残基的肽不被水解。脱酰胺酶的一些性质类似于组织蛋白酶a的报道。脱酰胺酶被二异丙基氟磷酸盐、凝乳胰蛋白酶类酶的抑制剂和汞化合物抑制，而其他阻断酶、胰蛋白酶类酶和金属蛋白酶的抑制剂无效。 In gel filtration, the native enzyme has an Mr = 94,000 while in non-reducing sodium dodecyl sulfate-polyacrylamide gel electrophoresis the Mr = 52,000 indicating it exists as a dimer. After reduction, deamidase dissociates into two chains of Mr = 33,000 and 21,000 as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. [3H]diisopropylfluorophosphate labeled the active site serine in the Mr = 33,000 chain. The first 25 amino acids of both chains were sequenced. They are identical with the sequences of the two chains of lysosomal "protective protein" which, in turn, has sequence similarity to the KEX1 gene product and carboxypeptidase Y of yeast. This protective protein complexes with beta-galactosidase and neuraminidase in lysosomes and is vitally important in maintaining their activity and stability. A defect in this protein is the cause of galactosialidosis, a severe genetic disorder. The ability of physiological stimuli (e.g. thrombin or collagen) to release the deamidase from platelets indicates that it may also be involved in the local metabolism of bioactive peptides.