Structure-function relationships of proteinase from soybean (Bowman-Birk) and lima bean: modification by N-acetylimidazole
Contributions of tyrosyl residues to trypsin- and chymotrypsin-inhibitory activities in two homologous proteinase inhibitors were investigated by modifying them with N-acetylimidazole under various conditions. In Bowman-Birk soybean proteinase inhibitor, Tyr 55, immediately following the antichymotryptic site Leu 53-Ser 54, is relatively inaccessible to N-acetylimidazole and can only be acetylated in the presence of 6 M guanidine hydrochloride but not in 8 M urea. The acetylation of Tyr 55 is accompanied by 60% loss in antichymotryptic activity. Deacetylation with hydroxylamine restores the activity to the original level. Tyr 69, located in the antitrypsin portion of the inhibitor, is relatively exposed to N-acetylimidazole and can be acetylated without denaturing agent. The acetylation of Tyr 69 parallels decrease in antitryptic activity. The inhibitor acetylated at Tyr 69 is fully active toward chymotrypsin and has 30 to 40% antitryptic activity of the native. The original level of antitryptic activity is restored upon deacetylation. Tyr 69 of lima bean proteinase inhibitor is relatively inaccessible to N-acetylimidazole: 75% acetylation in the presence of 6 M guanidine hydrochloride and 17% without the denaturing agent. The acetylated inhibitor is fully active toward chymotrypsin but retains only 29% (acetylated without guanidine hydrochloride) and 17% (acetylated with guanidine hydrochloride) of the original antitryptic activity. Deacetylation partially restores the lost antitryptic activity in the inhibitor acetylated without the denaturing agent.
- Research Organization:
- California Univ., Los Angeles (USA). Lab. of Nuclear Medicine and Radiation Biology
- DOE Contract Number:
- EY-76-C-03-0012
- OSTI ID:
- 6290140
- Report Number(s):
- UCLA-12-1167
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
59 BASIC BIOLOGICAL SCIENCES
ACETYLATION
ACYLATION
AMINES
AMINO ACIDS
AZOLES
BIOCHEMICAL REACTION KINETICS
CARBOXYLIC ACIDS
CHEMICAL REACTIONS
CHYMOTRYPSIN
DATA
DATA FORMS
ENZYME INHIBITORS
ENZYMES
EXPERIMENTAL DATA
FOOD
GRAPHS
HETEROCYCLIC COMPOUNDS
HYDROLASES
HYDROXY ACIDS
HYDROXYLAMINE
IMIDAZOLES
INFORMATION
ISOLATED VALUES
KINETICS
METABOLISM
NUMERICAL DATA
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PEPTIDE HYDROLASES
REACTION KINETICS
SOYBEANS
TRYPSIN
TYROSINE
VEGETABLES