Larger Intrinsic Rate Constants of Alphaamylase is Possible if Intrinsic Forward Rate Constant is ≠ Diffusion limited Rate of Encounter
Asian Journal of Chemical Sciences,
Page 114
DOI:
10.9734/ajocs/2022/v12i3219
Abstract
Background: Previous research has shown that the intrinsic reverse (backward) and forward rate constants are larger than the effective or apparent rate constants for the formation and dissociation of an enzymesubstrate complex (ES). It is speculated that such intrinsic rate constants could be larger if an appropriate mathematical equation was adopted for their computation.
Methods: Theoretical, experimental (Bernfeld method), and computational methods.
Objectives: 1) To rederive the equations for calculating the intrinsic rate constants for forward (k_{1}) and reverse (i.e., backward) (k_{2}) reactions; 2) to calculate the intrinsic rate constants; and 3) to show that the probability (1/g) (or r_{eq}(r)) that an enzyme is at a distance from the substrate is a variable.
Results and Discussion: The equations for the determination of k_{2} and k_{1} were rederived. Unlike previous findings, the intrinsic (reverse) first order rate, k_{2} and forward second order rate, k_{1} were larger than their apparent counterparts, but they were, however, very similar in magnitude. The intrinsic rate constants were much larger than previously reported values when the enzyme (E) total concentration [E_{T}] was much less than substrate’s total concentration [S_{T}]. The k_{1} and apparent forward second order rate (k_{f}) values where [E_{T}] is much less than [S_{T}] were > where [E_{T}] is less than [S_{T}]. Therefore, the magnitude of the second order rate constant is a function of [E_{T}]. The values of k_{1} and k_{2} where [E_{T}] is much less than [S_{T}] and viceversa were respectively, 7.41 exp. (+6) L/mol. min and 81.34 exp. (+4) /min, and 15.76 exp. (+6) L/mol. min and 58.08 exp.(+4) /min. It was discovered that the probability (1/g) (or r_{eq}(r))) that an enzyme is at a distance from the substrate with the possibility of mutual attraction is not constant.
Conclusion: If the intrinsic forward rate constant (k_{1}) is not equal to diffusion limited rate (k_{D}) of encounter, the k_{1} and k_{2} values could be larger than values where k_{1 }is equal to k_{D}. The probability (1/g) (or r_{eq}(r)) that an enzyme is at a distance from the substrate with the possibility of mutual attraction has been discovered to be a variable constant dependent on the concentration of the reaction mixture components and the enzyme's affinity for the substrate, and vice versa. Future research may attempt to derive an equation for the determination of an intrinsic catalytic rate constant for the formation of a product.
Keywords:
 Aspergillus oryzea alphaamylase
 apparent rate constants
 larger intrinsic rate constants
 intermolecular electrostatic potential energy
 the probability of intermolecular distance
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