Hydrolysis of human and pig brain natriuretic peptides, urodilatin, C-type natriuretic peptide and some C-receptor ligands by endopeptidase-24.11.
Hydrolysis of human and pig brain natriuretic peptides, urodilatin, C-type natriuretic peptide and some C-receptor ligands by endopeptidase-24.11.
复制标题
通过内肽酶 24.11 水解人和猪脑钠尿肽、尿舒张肽、C 型钠尿肽和一些 C 受体配体。
作者：
A. Kenny;A. Bourne;J. Ingram
内多肽酶-24.11 （E-24.11, EC 3.4.24.11）被广泛认为在代谢心房钠肽（ANP）中起生理作用。自ANP发现以来，新的利钠肽被分离出来，其他肽作为受体配体被合成。在体外研究了六种相关肽的内肽酶水解，主要是通过h.p.l.c。猪脑利钠肽（pBNP-32）的32位残基形式的初始攻击显示在Ser20-Leu21键上，正如之前显示的26位残基形式一样。相比之下，人脑利钠肽-32 （hBNP-32）与pBNP-32有10个残基不同，它首先在Met4-Val5键上受到攻击，释放n端四肽，然后才在环内的键上受到攻击：Arg17-Ile18和随后的其他四个位点。与α -人心房利钠肽-28 （α - hanp）相比，尿舒张素在n端有四个残基延伸，其降解速度约为后者的一半，尽管c端ph - arg - tyr的释放速度相同。22个残基的c型利钠肽的水解速度比α - hanp快，两个c受体配体（环内缺失的肽）：C-ANP4-23 （rANP4-23 des-Gln18,Ser19,Gly20,Leu21,Gly22）和SC 46542 （hANP5-28 des-Phe8,Gly9,Ala17,Gln18）。即使经过长时间的孵卵，血管紧张素转换酶也不能水解pBNP-32、hBNP-32或125i -大鼠(r) ANP。测定了E-24.11对α - hanp、猪BNP-26、猪BNP-32和125I-rANP的水解Km和kcat值。在以[125I]胰岛素B链或[125I] rANP为底物的E-24.11放射测定中，测定了α - hanp、尿扩张素、hBNP-32、c型利钠肽（CNP）、SC 46542和c型利钠肽（C-ANP4-23） 6种肽的Ki值。CNP的Ki值（2.5 ~ 13 microM）最低，而hBNP-32的Ki值（151 ~ 172 microM）最高。讨论了这些结果的生理意义，特别是关于hBNP-32对攻击的相对抗性以及c受体配体与利钠肽竞争被E-24.11水解的能力。
Endopeptidase-24.11 (E-24.11, EC 3.4.24.11) is widely believed to play a physiological role in metabolizing atrial natriuretic peptide (ANP). Since the discovery of ANP, new natriuretic peptides have been isolated and other peptides synthesized as receptor ligands. The hydrolysis in vitro of six related peptides by the endopeptidase has been studied, mainly by h.p.l.c. The initial attack on the 32-residue form of pig brain natriuretic peptide (pBNP-32) was shown to be at the Ser20-Leu21 bond, as had been previously shown for the 26-residue form. In contrast, human brain natriuretic peptide-32 (hBNP-32), which differs in ten residues from pBNP-32, was attacked first at the Met4-Val5 bond, releasing the N-terminal tetrapeptide, and only later at bonds within the ring: at Arg17-Ile18 and subsequently at four other sites. Urodilatin, which has a four-residue extension at the N-terminus compared with alpha-human atrial natriuretic peptide-28 (alpha-hANP), was degraded at about half the rate of the latter, though the C-terminal Phe-Arg-Tyr was released at the same rate. The 22-residue C-type natriuretic peptide was hydrolysed more rapidly than alpha-hANP, as were two C-receptor ligands (peptides with deletions within the ring): C-ANP4-23 (rANP4-23 des-Gln18,Ser19,Gly20,Leu21,Gly22) and SC 46542 (hANP5-28 des-Phe8,Gly9,Ala17,Gln18). Angiotensin-converting enzyme failed to hydrolyse pBNP-32, hBNP-32 or 125I-rat (r) ANP, even after prolonged incubation. Km and kcat values were determined for the hydrolysis of alpha-hANP, porcine BNP-26, porcine BNP-32 and 125I-rANP by E-24.11. Ki values were determined for six peptides, alpha-hANP, urodilatin, hBNP-32, C-type natriuretic peptide (CNP), SC 46542 and C-type natriuretic peptide (C-ANP4-23), in radiometric assays of E-24.11 with either [125I] insulin B chain or [125I] rANP as substrate. The Ki values (2.5-13 microM) for CNP were the lowest of any of the group, whereas those for hBNP-32 (151-172 microM) were the highest. The physiological significance of these results is discussed, especially in regard to the relative resistance of hBNP-32 to attack and the ability of the C-receptor ligands to compete with natriuretic peptides for hydrolysis by E-24.11.