人血小板中的一种肽酶，能脱速激肽。可能与溶酶体“保护蛋白”相同。
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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，能脱速激肽。可能与溶酶体“保护蛋白”相同。
中华生物化学杂志，1990年7月5日;26(19):11265-72。
- PubMed ID
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1694176 (PubMed视图］
- 摘要
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我们在人类血小板中发现了一种酶，它能脱氨P物质和其他速激肽。由于氨基化羧基末端对生物活性很重要，我们纯化并鉴定了这种脱酰胺酶。该酶由凝血酶从人血小板中释放，经硫酸铵沉淀纯化至均匀，然后在辛基sepharose柱上进行层析，并以PBE 94为聚焦。纯化的酶具有酯酶、肽酶和脱酰胺酶活性。肽酶(含呋喃丙烯酰- phe - phe)在pH 5.0时活性最佳，而酯酶(苯甲酰-酪氨酸乙基酯)和脱酰胺酶(D-Ala2-Leu5-enkephalinamide)在pH 7.0时活性最佳。对于生物学上重要的多肽，该酶既作为脱酰胺酶(P物质，神经激肽a和eledoisin)，也作为羧肽酶(与缓激肽，血管紧张素I, P物质游离酸，无催产素酸)处于中性状态，尽管羧肽酶在pH值5.5时作用更快。脑啡肽在脑啡胺去酰胺化后释放，不裂解。催产素的Gly9-NH2被释放而不去酰胺化。精氨酸残基倒数第二的肽不能水解。脱酰胺酶的某些性质与组织蛋白酶a的性质相似。脱酰胺酶被氟磷酸二异丙基、胰糜蛋白酶类酶抑制剂和汞化合物抑制，而导管酶、胰蛋白酶类酶和金属蛋白酶的其他抑制剂无效。 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.