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The Proflavin-Induced Increase in the Catalytic Activity of Ficin.
- Source :
-
European Journal of Biochemistry . 1968, Vol. 5 Issue 3, p366-375. 10p. - Publication Year :
- 1968
-
Abstract
- The dye proflavin (3,6 diaminoacridine) binds to a single site on the ficin molecule (EC 3.4.4.12). The value of the dissociation constant (Kp) for the enzyme-dye complex was 3.5±1.8 × 10-4 M measured spectrophotometrically and 1.55± 0.61 × 10-4 by equilibrium dialysis. Interaction with proflavin increased the catalytic constant (kcat) for the ficin-catalysed hydrolysis of benzoyl-L-arginine ethyl ester although the value of KM app was unaltered. Dye-binding did not significantly affect the value of kcat for the ficin-catalysed hydrolysis of p-nitrophenyl hippurate, a substrate for which acylation is not rate-limiting in catalysis. The dependence of initial velocity of benzoyl-L-arginine ethyl ester hydrolysis on dye concentration enabled the computation of a value of Kp=1.61 7times; 10-4 M assuming a kinetic model involving formation of a ternary dye-enzyme-substrate complex in which substrate is more rapidly hydrolyzed than in the binary enzyme-substrate complex. Dye-binding leads to an enhanced nucleophilicity of the essential thiol group of ficin. It is concluded that deacylation is not the rate-limiting step in the ficin-catalysed hydrolysis of benzoyl-L-arginine ethyl ester. Possible explanations of the proflavin-induced acceleration of benzoyl L-arginine ethyl ester hydrolysis by ficin are discussed, including consideration of an allosteric modification mechanism. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 00142956
- Volume :
- 5
- Issue :
- 3
- Database :
- Academic Search Index
- Journal :
- European Journal of Biochemistry
- Publication Type :
- Academic Journal
- Accession number :
- 12791027
- Full Text :
- https://doi.org/10.1111/j.1432-1033.1968.tb00379.x