Multiplicities and some enzymatic characteristics of ape pepsinogens and pepsins

Pepsinogen levels in ape stomachs were comparable to those in macaques and significantly higher than those in the stomachs of other mammals, including carnivores and ruminants. The occurrence of multiple forms of pepsinogens was remarkable. Nine, sixteen, eight, and fourteen pepsinogens were purified or partially purified from the gastric mucosa of a gibbon, orang-utan, gorilla, and chimpanzee, respectively. Most of these were type-A pepsinogens, and only one type-C pepsinogen was identified in each ape. The two types could be readily distinguished by staining for proteolytic activity on polyacrylamide gel electrophoresis (PAGE) in the presence/absence of pepstatin. Type-A pepsinogens were further divided into two subtypes. One subtype, constituting a major group of pepsinogens in apes, exhibited high hemoglobin-digestive activity. The other subtype was specified by a relatively high content of Lys and low hemoglobin-digestive activity. It is likely that pepsinogen-A genes have been duplicated several times as hominoids, including humans, evolved in the primate lineage. The presence of multiple pepsinogens in apes might be advantageous in the efficient digestion of a wide variety of foods.