Baudin B, Giboudeau J
Laboratoire de Biochimie A, Hôpital Saint-Antoine, Paris, France.
Enzyme Protein. 1994;48(2):81-9. doi: 10.1159/000474973.
We compared angiotensin I-converting enzyme (ACE) and carboxypeptidase A (CPA), two zinc metallopeptidases, for the hydrolysis of the usual ACE synthetic substrate benzoylglycyl-histidyl-leucine (HHL) investigating the possible interference by CPA in the determination of ACE activity in biological fluids. Both purified enzymes hydrolyse HHL in a radiochemical assay with the same optimal pH, a characteristic divalent metal requirement, a close similar behavior against inhibitors of other metallopeptidases, such as enkephalinase and kininase I, and the involvement of arginine and lysine residues in their active site. Conversely, CPA does not show the other catalytic properties of ACe, i.e. chloride dependence, low Km for HHL, inhibition by specific synthetic ACE inhibitors and antibody, also hydrolysis of the other ACE substrate furylacryloylphenylalanyl-glycyl-glycine (FAPGG). We advise the use of ACE inhibitors to validate ACE measurement with HHL or, alternatively, FAPGG, which is a more specific substrate for ACE, must be preferred, although the poor sensitivity of the spectrophotometric assay with this substrate limits its use to blood samples.
我们比较了两种锌金属肽酶——血管紧张素I转换酶（ACE）和羧肽酶A（CPA）对常用的ACE合成底物苯甲酰甘氨酰 - 组氨酰 - 亮氨酸（HHL）的水解作用，研究CPA在生物体液中ACE活性测定中可能产生的干扰。在放射化学分析中，两种纯化的酶都能水解HHL，它们具有相同的最佳pH值、对二价金属的特定需求、对其他金属肽酶抑制剂（如脑啡肽酶和激肽酶I）的类似反应，以及其活性位点中精氨酸和赖氨酸残基的参与。相反，CPA不具有ACE的其他催化特性，即对氯离子的依赖性、对HHL的低Km值、被特定合成ACE抑制剂和抗体抑制，以及对另一种ACE底物呋喃丙烯酰苯丙氨酰 - 甘氨酰 - 甘氨酸（FAPGG）的水解作用。我们建议使用ACE抑制剂来验证用HHL进行的ACE测量，或者，作为替代方法，必须优先选择FAPGG，它是ACE更特异的底物，尽管用该底物进行分光光度测定的灵敏度较差，限制了其仅用于血液样本。
