Liver alcohol dehydrogenase-coenzyme reaction rates.

DeTraglia, Michael C.; Schmidt, Jack; Dunn, Michael F.; McFarland, James T.

doi:10.1016/s0021-9258(17)40418-2

Cited by 39 publications

(12 citation statements)

References 20 publications

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“…At pH values above 7 (Fernley & Walker, 1966), phosphatase must be kinetically limited in the steady state by the rate of dissociation of tightly and noncovalently bound product. In this regard, it resembles a number of dehydrogenases (Raval & Wolfe, 1962;Silverstein & Sulebele, 1969;Heck, 1969;DiFranco & Iwatsubo, 1971; Shore & Gutfreund, 1970; Czeisler & Hollis, 1973;DeTraglia et al, 1977). Several kinases may also observe this behavior (Nageswara Rao et al, 1976Rao et al, , 1978aRao et al, ,b, 1979.…”

Section: Discussionmentioning

confidence: 94%

Catalytic mechanism of Escherichia coli alkaline phosphatase: resolution of three variants of the acyl-enzyme mechanism

Bloch¹,

Gorby²

1980

Biochemistry

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Three variants of the classical acyl-enzyme mechanism were compared theoretically with respect to the predicted transient kinetics of substrate hydrolysis by Escherichia coli alkaline phosphatase. In all three, acyl-enzyme hydrolysis was assumed to exist initially primarily as a noncovalent complex with the acid product, inorganic phosphate. In one mechanism, the pre-steady-state rate-controlling step was assumed to be the dissociation of acid product from its initial complex with enzyme. In the other two, pre-steady-state rate control was assigned to an enzyme isomerization occurring before or after substrate binding to free enzyme. Under concentration conditions of excess substrate and acid product, integrated rate laws were used to reject the possibility of pre-steady-state rate control by enzyme isomerization between phosphate dissociation and substrate binding. Whereas this mechanism predicts a pre-steady-state noncompetitive relationship between substrate and acid product, the stopped-flow kinetics of 4-methylumbelliferyl phosphate hydrolysis demonstrates a competitive relationship, consistent with either of the other two mechanisms. Under concentration conditions of stoichiometrically limiting substrate, computer simulations eliminated the possibility of rate control by enzyme isomerization after substrate binding. This mechanism predicts a substrate concentration dependence for the apparent first-order rate constant of substrate hydrolysis which disagrees with previously published data [Halford, S. E. (1971) Biochem. J. 125, 319--327]; the other two mechanisms are consistent with experiment. Comparison of transient kinetic theory and experiment under these two contrasting concentration conditions suggests strongly that the rate-controlling step in phosphate ester hydrolysis by E. coli alkaline phosphate is the dissociation of "sticky" acid product from its noncovalent complex with enzyme. This mechanism explains an anomaly in the stopped-flow kinetic trace, a substoichiometric pre-steady-state burst of alcohol product release.

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Section: Discussionmentioning

confidence: 94%

Catalytic mechanism of Escherichia coli alkaline phosphatase: resolution of three variants of the acyl-enzyme mechanism

Bloch¹,

Gorby²

1980

Biochemistry

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“…Furthermore, kinetics of NAD"1" association were investigated in the absence of any substrate analogue. This reaction was studied at pH 9 and above as both association and dissociation rate constants for NAD+ are known to be slower at higher pH (Detraglia et al, 1977;Kvassman & Pettersson, 1979). Figure 2 shows that apparent rate constants for NAD+ binding are a function of NAD"1" concentration at pH 10.…”

Section: Resultsmentioning

confidence: 99%

“…edge no evidence of a pK value less than 7 has been obtained (Detraglia et al, 1977;Kvassman & Pettersson, 1979;Pettersson, 1987). Steady-state kinetics, however, suggest a pK in this region (Dalziel, 1963).…”

Section: E-nad-pyrazolementioning

confidence: 99%

Mechanism of binding of horse liver alcohol dehydrogenase and nicotinamide adenine dinucleotide

Sekhar¹,

Plapp²

1988

Biochemistry

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The binding of NAD+ to liver alcohol dehydrogenase was studied by stopped-flow techniques in the pH range from 6.1 to 10.9 at 25 degrees C. Varying the concentrations of NAD+ and a substrate analogue used to trap the enzyme-NAD+ complex gave saturation kinetics. The same maximum rate constants were obtained with or without the trapping agent and by following the reaction with protein fluorescence or absorbance of a ternary complex. The data fit a mechanism with diffusion-controlled association of enzyme and NAD+, followed by an isomerization with a forward rate constant of 500 s-1 at pH 8: E E-NAD+ *E-NAD+. The isomerization may be related to the conformational change determined by X-ray crystallography of free enzyme and enzyme-coenzyme complexes. Overall bimolecular rate constants for NAD+ binding show a bell-shaped pH dependence with apparent pK values at 6.9 and 9.0. Acetimidylation of epsilon-amino groups shifts the upper pK to a value of 11 or higher, suggesting that Lys-228 is responsible for the pK of 9.0. Formation of the enzyme-imidazole complex abolishes the pK value of 6.9, suggesting that a hydrogen-bonded system extending from the zinc-bound water to His-51 is responsible for this pK value. The rates of isomerization of E-NAD+ and of pyrazole binding were maximal at pH below a pK of about 8, which is attributable to the hydrogen-bonded system. Acetimidylation of lysines or displacement of zinc-water with imidazole had little effect on the rate of isomerization of the E-NAD+ complex.(ABSTRACT TRUNCATED AT 250 WORDS)

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“…Conditions on the Gibson-Durrum stopped-flow spectrophotometer were identical with those reported in the NAD4" dissociation experiment. 14 The following buffers were used in the pH dependence studies: pH 6.0-7.5, 0.1 M phosphate buffer; pH 7.5-9.0, 0.05 M pyrophosphate buffer; pH 9.0-10.5, 0.1 M carbonate buffer.…”

Section: Methodsmentioning

confidence: 99%