DIPEPTIDYLPEPTIDASE-IV AND TRYPSIN-LIKE ENZYMATIC DEGRADATION OF HUMAN GROWTH-HORMONE RELEASING HORMONE IN PLASMA
DIPEPTIDYLPEPTIDASE-IV AND TRYPSIN-LIKE ENZYMATIC DEGRADATION OF HUMAN GROWTH-HORMONE RELEASING HORMONE IN PLASMA
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DOI：
10.1172/jci114049
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发表时间：
1989-05-01
影响因子：
15.9
通讯作者：
FELIX, AM
中科院分区：
文献类型：
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作者：
FROHMAN, LA;DOWNS, TR;FELIX, AM
研究了在2-3个氨基酸键处负责生长激素释放激素（GRH）初级蛋白水解裂解的血浆酶。原生GRH[GRH(1-44)-NH2和GRH(1-40)-OH]和cooh末端缩短片段[GRH(1-32)-NH2和GNRH(1-29)-NH2]被快速切割，而GRH(2-32)-NH2在该位点未被降解。此外，对GRH(3-44)-NH2的降解不受氨肽酶抑制剂的影响，这表明这种代谢物是由二肽基肽酶（DPP）的单步裂解产生的，而不是由连续的氨肽酶裂解产生的。GRH(3-44)-NH2的转化被二蛋白A阻断，二蛋白A是DPP IV型（DPP IV）竞争抑制剂。在1号或2号位置的d -氨基酸取代也阻止了水解，这是DPP IV的特征。对人GRH转基因猪内源性血浆GRH免疫反应性的分析表明，GRH(3-44)-NH2是主要的峰。天然GRH在11-12位点表现出胰蛋白酶样降解，而在12-13位点只有GRH(1-32)-NH2和GRH(1-29)-NH2发生裂解。这些代谢物的形成与先前的DPP IV水解无关，但被胰蛋白酶抑制剂大大减少。对潜在GRH超级类似物的血浆稳定性评估证实，GRH在血浆中的降解主要由DPP IV进行，并在较小程度上由胰蛋白酶样酶进行。
The plasma enzyme responsible for primary proteolytic cleavage of growth hormone-releasing hormone (GRH) at the 2-3 amino acid bond was characterized. Native GRH[GRH(1-44)-NH2 and GRH(1-40)-OH], and COOH-terminally shortened fragments [GRH(1-32)-NH2 and GNRH(1-29)-NH2] were rapidly cleaved, while GRH(2-32)-NH2 was not degraded at this site. Moreover, degradation to GRH(3-44)-NH2 was unaffected by an aminopeptidase inhibitor, indicating that this metabolite was generated from a single step cleavage by a dipeptidylpeptidase (DPP) rather than sequential aminopeptidase cleavages. Conversion to GRH(3-44)-NH2 was blocked by diprotein A, a DPP type IV (DPP IV) competitive inhibitor. D-Amino acid substitution at either position 1 or 2 also prevented hydrolysis, characteristic of DPP IV. Analysis of endogenous plasma GRH immunoreactivity from a human GRH transgenic pig revealed that the major peak coeluted with GRH(3-44)-NH2. Native GRH exhibited trypsin-like degradation at the 11-12 position but cleavage at the 12-13 site occurred only with GRH(1-32)-NH2 and GRH(1-29)-NH2. Formation of these metabolites was independent of prior DPP IV hydrolysis but was greatly reduced by trypsin inhibitors. Evaluation of plasma stability of potential GRH super analogues, designed to resist degradation by these enzymes, confirmed that GRH degradation in plasma occurs primarily by DPP IV, and to a lesser extent by trypsin-like enzyme(s).