Primate food habits and-diversity of pepsinogens

从4种成年新大陆恒河猴(Caltithrix Jacchus)、棉铃猴(Saguinus Odipus)、松鼠猴(Saimiri Scureus)和卷尾猴(Cebus Paella)中分离纯化了胃蛋白酶原A、C和前凝乳素。原凝乳酶的出现是非常独特的，因为这种酶原已知是新生儿特有的，在灵长类动物中，原凝乳酶基因被认为是不起作用的。除了在卷尾猴身上发现了两个胃蛋白酶原-A同工酶基因外，没有在每种类型的胃蛋白酶原中检测到多种形式。在pH 2~2.5范围内，A、C和凝乳酶对血红蛋白的最适水解度分别为20、30和15个单位/mg蛋白质。在等摩尔量的胃抑素存在下，胃蛋白酶A被抑制，而凝乳酶和胃蛋白酶C分别需要摩尔过量5倍和100倍的胃抑素才能完全抑制。在胃蛋白酶A和凝乳酶中，胰岛素B链首先发生在Leul5-Tyr16键上，而在胃蛋白酶C中，胰岛素B链首先发生在Leu15-Tyr16或Tyr16-Leu17键上。基于核苷酸序列的胃蛋白酶原系统发育树显示，普通绒猴在大约4000万年前就与祖先灵长类动物背道而驰。

Pepsinogens A and C, and prochymosin were purified from 4 species of adult New World monkeys, namely, common marmoset (Caltithrix jacchus), cotton-top tamarin (Saguinus oedipus), squirrel monkey (Saimiri sciureus), and capuchin monkey (Cebus paella). Occurrence of prochymosin was quite unique since this zymogen is known to be neonate-specific, and in primates it has been thought that prochymosin gene is not functional. No multiple form has been detected in each type of pepsinogen except that two pepsinbgen-A isozymogens were identified in capuchin monkey. Pepsins A and C, and chymosin hydrolyzed hemoglobin optimally at pH 2-2.5 with the maximal activities of about 20, 30, and 15 units/mg protein. Pepsins A were inhibited in the presence of an equimolar amount of pepstatin, and chymosins and pepsins C needed 5- and 100-fold molar excess of pepstatin for the complete inhibition, respectively. Hydrolysis of insulin B chain was occurred first at Leul5-Tyrl6 bond in the case of pepsins A and chymosins, and at either Leu15-Tyr16 or Tyr16-Leu17 bonds in the case of pepsins C. Molecular cloning of cDNAs for three types of pepsinogens from common marmoset was achieved. A phylogenetic tree of pepsinogens based on the nucleotide sequence showed that common marmoset has diverged from the ancestral primate about 40 million years ago.