Kerfelec B, Chapus C, Puigserver A
Eur J Biochem. 1985 Sep 16;151(3):515-9. doi: 10.1111/j.1432-1033.1985.tb09132.x.
The existence of procarboxypeptidase A, in the form of a non-covalent ternary complex containing the apparently inactive serine protease (subunit III), has so far been observed only in the ox pancreas. Evidence, obtained in the present study, shows that a ternary complex of procarboxypeptidase A, with a subunit III highly homologous with that of the bovine complex, is also present in two other ruminant species, sheep and goat. The biological significance of these complex forms of procarboxypeptidase A and the consistently high biosynthesis level of the apparently inactive subunit III in all three ruminant species is still unknown. Yet the synthesis of subunit III is not related to the animal diet since in the horse, which is a non-ruminant herbivorous animal, the procarboxypeptidase A is monomeric. Reassociation assays between either bovine subunits II or III and monomeric as well as binary forms of procarboxypeptidase A from various species show that, unlike subunit II, the recognition site for subunit III is highly conserved in all the procarboxypeptidases A and that bovine subunit II is different from porcine chymotrypsinogen C with regard to association.
羧肽酶原A以一种非共价三元复合物的形式存在，其中包含明显无活性的丝氨酸蛋白酶（亚基III），迄今为止仅在牛胰腺中观察到。本研究获得的证据表明，羧肽酶原A的三元复合物，其亚基III与牛复合物的亚基III高度同源，也存在于另外两种反刍动物，绵羊和山羊中。这些羧肽酶原A复杂形式的生物学意义以及在所有三种反刍动物中明显无活性的亚基III持续保持的高生物合成水平仍然未知。然而，亚基III的合成与动物饮食无关，因为在作为非反刍食草动物的马中，羧肽酶原A是单体形式。来自各种物种的牛亚基II或III与羧肽酶原A的单体及二元形式之间的重缔合试验表明，与亚基II不同，亚基III的识别位点在所有羧肽酶原A中高度保守，并且牛亚基II在缔合方面与猪胰凝乳蛋白酶原C不同。
