Primate food habits and-diversity of pepsinogens

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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.