title: Novel peptide inhibitor (SPAI) of Na+, K+-ATPase from porcine intestine.
abstract: Three unique inhibitors (SPAI-1, -+2, and -3) were first purified from porcine duodenal extract based on the Na+, K+-ATPase inhibitory activity. These peptide inhibitors had four disulfide bridges in common. The sequencing results of their S-carboxymethyl derivatives, lysilendopeptidase fragments, and chymotryptic peptides disclosed their entire primary structures. Both SPAI-2 and -3 consisted of 61 amino acids, respectively, and had almost the same sequences except for two amino acid substitutions, while SPAI-1 was found to lack the N-terminal twelve amino acid sequence of SPAI-2. The kinetics study revealed that SPAIs inhibited Na+, K+-ATPase by the competitive mode against Na+ and were uncompetitive with K+.
authors.affiliation: Tsukuba Research Laboratories, Eisai Co., Ltd., Japan.
authors.forename: K
authors.initials: K
authors.lastname: Araki
authors.forename: J
authors.initials: J
authors.lastname: Kuroki
authors.forename: O
authors.initials: O
authors.lastname: Ito
authors.forename: M
authors.initials: M
authors.lastname: Kuwada
authors.forename: S
authors.initials: S
authors.lastname: Tachibana
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D000818:Animals; D036341:Intercellular Signaling Peptides and Proteins; D007422:Intestines / Q000201:enzymology*; D008969:Molecular Sequence Data; D011506:Proteins / Q000494:pharmacology*; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D013552:Swine
chemical_list: D000596:Amino Acids; D036341:Intercellular Signaling Peptides and Proteins; D011506:Proteins; C061401:SPAI-1 protein, Sus scrofa; C061403:SPAI-3 protein, Sus scrofa; C061402:SPAI-2 protein, Sus scrofa; D000254:Sodium-Potassium-Exchanging ATPase