title: Tryptic cleavage as a probe of conformational differences between active and inactive forms of ornithine aminotransferase.
abstract: Treatment of ornithine aminotransferase with trypsin resulted in rapid and complete loss of enzyme activity in a process that coincided with a reduction in subunit Mr of about 3000. However, electrophoresis showed that a substantial proportion of the enzyme had not been digested. The component of the preparation of ornithine aminotransferase that was insusceptible to trypsin contained a naturally occurring but enzymically inactive form of the enzyme, and when this had been removed, the remaining fully active enzyme was completely digested. Irreversible inactivation with a substrate analogue made all of the enzyme insusceptible to trypsin. The hydrolyzed enzyme still underwent a very slow half-reaction with ornithine. Sequence analysis of the truncated protein, prepared by blotting from electrophoretic gels, showed that hydrolysis had occurred at peptide bond Lys26-Tyr27.
authors.affiliation: Department of Biochemistry, University College, Cardiff, Wales, United Kingdom.
authors.forename: M
authors.initials: M
authors.lastname: Simmaco
authors.forename: L
authors.initials: L
authors.lastname: Carr
authors.forename: F
authors.initials: F
authors.lastname: Bossa
authors.forename: D
authors.initials: D
authors.lastname: Barra
authors.forename: J M
authors.initials: JM
authors.lastname: Basford
authors.forename: R A
authors.initials: RA
authors.lastname: John
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D004789:Enzyme Activation; D007700:Kinetics; D008969:Molecular Sequence Data; D009952:Ornithine / Q000378:metabolism; D009953:Ornithine-Oxo-Acid Transaminase / Q000037:antagonists & inhibitors / Q000378:metabolism; D010446:Peptide Fragments / Q000032:analysis; D011487:Protein Conformation; D051381:Rats; D000637:Transaminases / Q000037:antagonists & inhibitors / Q000378:metabolism; D014357:Trypsin / Q000494:pharmacology*
chemical_list: D010446:Peptide Fragments; D009952:Ornithine; D000637:Transaminases; D009953:Ornithine-Oxo-Acid Transaminase; D014357:Trypsin