title: Cleavage of peptide bonds bearing ionizable amino acids at P(1) by serine proteases with hydrophobic S(1) pocket.
abstract: Enzymatic hydrolysis of the synthetic substrate succinyl-Ala-Ala-Pro-Xxx-pNA (where Xxx=Leu, Asp or Lys) catalyzed by bovine chymotrypsin (CHYM) or Streptomyces griseus protease B (SGPB) has been studied at different pH values in the pH range 3-11. The pH optima for substrates having Leu, Asp, and Lys have been found to be 7.5-8.0, 5.5-6.0, and ∼10, respectively. At the normally reported pH optimum (pH 7-8) of CHYM and SGPB, the substrate with Leu at the reactive site is more than 25,000-fold more reactive than that with Asp. However, when fully protonated, Asp is nearly as good a substrate as Leu. The pK values of the side chains of Asp and Lys in the hydrophobic S(1) pocket of CHYM and SGPB have been calculated from pH-dependent hydrolysis data and have been found to be about 9 for Asp and 7.4 and 9.7 for Lys for CHYM and SGPB, respectively. The results presented in this communication suggest a possible application of CHYM like enzymes in cleaving peptide bonds contributed by acidic amino acids between pH 5 and 6.
authors.affiliation: Department of Chemistry, Indiana University Purdue University Fort Wayne, 2101 E. Coliseum Blvd., Fort Wayne, IN 46805, USA. qasimm@ipfw.edu
authors.forename: Mohammad A
authors.initials: MA
authors.lastname: Qasim
authors.forename: Jikui
authors.initials: J
authors.lastname: Song
authors.forename: John L
authors.initials: JL
authors.lastname: Markley
authors.forename: Michael
authors.initials: M
authors.lastname: Laskowski
mesh_terms: D000596:Amino Acids / Q000737:chemistry*; D000818:Animals; D002417:Cattle; D002918:Chymotrypsin / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D057927:Hydrophobic and Hydrophilic Interactions; D010455:Peptides / Q000737:chemistry*; D012697:Serine Endopeptidases / Q000737:chemistry*
chemical_list: D000596:Amino Acids; D010455:Peptides; D012697:Serine Endopeptidases; D002918:Chymotrypsin; C024984:streptogrisin B
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