Feracci H, Benajiba A, Gorvel J P, Doumeng C, Maroux S
Biochim Biophys Acta. 1981 Mar 13;658(1):148-57. doi: 10.1016/0005-2744(81)90258-8.
Immunological homology was shown between the active site regions of pig and rabbit aminopeptidases N and between those of the corresponding aminopeptidases A. However, no homology was detectable between the aminopeptidases N and A (EC 3.4.11.-) in a given species. The dimeric structure of pig aminopeptidases did not significantly modify their catalytic properties in aqueous solution compared to those of the monomeric rabbit enzymes. Only a slight difference in binding conditions was noted in the case of aminopeptidases N. Aminopeptidase A activity towards acidic substrates was enhanced by physiological concentrations of Ca2+ while that towards neutral substrates was considerably reduced. Therefore, acidic amino acid residues in proteins and peptides may be assumed to be mostly split off in vivo by aminopeptidase A, neutral residues by aminopeptidases N and basic residues by both enzymes. The respective specificity of aminopeptidase A and N for acidic and neutral amino acid residues was found to be mainly due to a more productive binding mode of the substrate rather than to a better affinity.
猪和兔氨肽酶N的活性位点区域之间以及相应氨肽酶A的活性位点区域之间均显示出免疫同源性。然而，在给定物种中，氨肽酶N和A（EC 3.4.11.-）之间未检测到同源性。与单体兔酶相比，猪氨肽酶的二聚体结构在水溶液中并未显著改变其催化特性。仅在氨肽酶N的情况下，观察到结合条件存在细微差异。氨肽酶A对酸性底物的活性在生理浓度的Ca2+作用下增强，而对中性底物的活性则显著降低。因此，可以推测蛋白质和肽中的酸性氨基酸残基在体内主要由氨肽酶A裂解，中性残基由氨肽酶N裂解，碱性残基则由这两种酶共同裂解。发现氨肽酶A和N对酸性和中性氨基酸残基的各自特异性主要归因于底物更有效的结合模式，而非更好的亲和力。
