Isolation and characterization of sheep pepsin.
Sheep pepsin was isolated (approx. 120-fold purification) from aqueous abomasal homogenates by (1) pH fractionation, (2) chromatography on Sepharose 4B-poly-L-lysine columns and (3) gel filtration on Sephadex G-100. The enzyme had mol.wt. approx. 34000, N-terminal valine and C-terminal alanine. The amino acid composition of sheep pepsin was generally similar to that of pig and ox pepsins, with a very low content of basic residues and a high content of acidic and hydroxy-amino acids. The pH optimum for NN-dimethyl-casein and NN-dimethyl-haemoglobin as substrates was approx. 1.8. The Km and kcat. for NN-dimethyl-haemoglobin were 46micronM and 1100min-1 respectively, and for NN-dimethyl-casein the corresponding parameters were 50micronM and 420min-1. These values were generally similar to those for pig and ox pepsins. At the pH optimum of 4.6, the sheep pepsin was about 50% as active on benzyloxycarbonyl-L-histidyl-L-phenyl-alanyl-L-tryptophan ethyl ester as was pig pepsin. The pH optimum for the hydrolysis of N-acetyl-L-phenylalanyl-L-di-iodotyrosine by sheep, ox and pig pepsins was approx. 1.85.
D000596:Amino Acids / Q000032:analysis; D000818:Animals; D002364:Caseins / Q000031:analogs & derivatives; D002417:Cattle; D002846:Chromatography, Affinity; D002850:Chromatography, Gel; D006454:Hemoglobins; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007700:Kinetics; D008970:Molecular Weight; D010434:Pepsin A / Q000302:isolation & purification*; D010750:Phosphoproteins / Q000032:analysis; D012756:Sheep; D013552:Swine
D000596:Amino Acids; D002364:Caseins; D006454:Hemoglobins; D010750:Phosphoproteins; D010434:Pepsin A