Amphibian pepsinogens: purification and characterization of xenopus pepsinogens, and molecular cloning of Xenopus and bullfrog pepsinogens.
Two pepsinogens (Pg C and Pg A) were isolated from the stomach of adult Xenopus laevis by Q-Sepharose, Sephadex G-75, and Mono-Q column chromatographies. Autolytic conversion and activation of the purified Pgs into the pepsins were examined by acid treatment. We determined the amino acid sequences from the NH2-termini of Pg C, pepsin C, Pg A, and pepsin A. Based on the sequences, the cDNAs for Pg C and Pg A were cloned from adult stomach RNA, and the complete amino acid sequences of the Pg C and Pg A were predicted. In addition, a Pg A cDNA was cloned from the stomach of adult bullfrog Rana catesbeiana, and the primary structure of the Pg A was predicted. Molecular phylogenetic analysis showed that such anuran Pg C and Pg A belong to the Pg C group and the Pg A group in vertebrates, respectively. The molecular properties of Pg C and Pg A, such as size, sequences of the activation peptide and active site, profile of autolytic activation, and pH dependency of proteolytic activity of the activated forms, pepsin C and pepsin A, resemble those of Pgs found in other vertebrates. However, the hemoglobin-hydrolyzing activity of Xenopus pepsin C is completely inhibited in the presence of equimolar pepstatin, an inhibitor of aspartic proteinases. Thus, the Xenopus pepsin C differs significantly from other vertebrate pepsins C in its high susceptibility to pepstatin, and closely resembles A-type pepsins.
Ikuzawa
M
M
Life Science Institute, Sophia University, Kioi-cho Chiyoda-ku, Tokyo 102-8554, Japan.
Inokuchi
T
T
Kobayashi
K
K
Yasumasu
S
S
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000032:analysis; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D010434:Pepsin A / Q000235:genetics / Q000378:metabolism; D020116:Pepsinogen A / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D020115:Pepsinogen C / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D010802:Phylogeny; D011892:Rana catesbeiana; D014982:Xenopus laevis
D018076:DNA, Complementary; D020115:Pepsinogen C; D020116:Pepsinogen A; D010434:Pepsin A