Triose phosphate isomerase catalysis

In what is now a classical study in enzyme kinetics, W. J. Albery and J. R Knowles developed a strategy for establishing a reaction coordinate diagram (shown in Fig. 2) for triose-phosphate isomerase catalysis using solvent exchange and kinetic isotope effect data. 

S. Blacklow, R. Raines, W. Lim, P. Zamore, and J. Knowles, Biochemistry, 27, 1158 (1988). Triose Phosphate Isomerase Catalysis Is Diffusion Controlled. 

Knowles, J., and Albery, W., 1977. Perfection in enzyme catalysis The energetics of triose phosphate isomerase. Accounts of Chemical Research 10 105-111. 

Triose phosphate isomerase enotization via acid-base catalysis... 

Figure 2. Free energy profile for converting di hydroxy acetone phosphate, the substrate (abbreviated S) and glyceraldehyde 3-phosphate, the product (abbreviated P), with intermediate formation of the enedi-olate (abbreviated Z). Catalysis occurs either by a free carboxyl group (levels connected by dotted lines) or by triose-phosphate isomerase (levels connected by dashed lines). The vertical arrows show the limits of those states that are less well defined as a result of uncertainty in the experimental data. The transition state marked "e" refers to the exchange of protons between the solvent and the enzyme-bound enediol intermediate (EZ). Reproduced with permission of the authors and the American Chemical Society.

Creighton and Murthy recently reviewed the stereochemistry and related mechanistic issues associated with enzyme-catalyzed isomerizations that proceed by 1,2-hydrogen transfer or by 1,3-aUytic hydrogen transfer. In the first case, the prototypical aldose-ketose isomerase is triose-phosphate isomerase (or TPl), an enzyme that uses the carboxylate of Glu-165 as a base for abstracting a proton from the substrate during catalysis. A -3-Keto-... 

The importance of binding energy to catalysis can be readily demonstrated. For example, the glycolytic enzyme triose phosphate isomerase catalyzes the interconversion of glyceraldehyde 3-phosphate and dihy-droxyacetone phosphate ... 

Chapter 8, How Enzymes Work, starts with a description of the basic chemical mechanisms that are exploited by enzymes. The latter half of this chapter presents a detailed description of how three enzymes—chymotrypsin, RNase, and triose phosphate isomerase—exploit these basic mechanisms of enzyme catalysis. 

Enzyme Mechanisms.— Triose phosphate isomerase has been a popular enzyme recently, having been the chief example quoted in two reviews on perfection and efficiency in enzyme catalysis - and the subject of seven successive papers in one issue of Biochemistry including one on the evolution of enzyme function and the development of catalytic efficiency. During glycolysis in muscle, fructose 1,6-bisphos-... 

The active site of triose phosphate isomerase is complementary, in both stereochemistry and charge configuration, to the transition state of the reaction it catalyses. This fact, combined vith very efficient general base catalysis, is largely responsible for the high efficiency of TIM. 

N. S. Sampson and J. R. Knowles, Biochemistry, 31, 8482 (1992). Segmental Movement Definition of the Structural Requirements for Loop Closure in Catalysis by Triose Phosphate Isomerase. 

E. Lolis and G. Petsko, Biochemistry, 29, 6619 (1990). Crystallographic Analysis of the Complex Between Triose Phosphate Isomerase and 2-Phosphoglycolate at 2.5 A Resolution Implications for Catalysis. 

Figure 8.49 Mechanisms of three enzymes that utilise general acid-base catalysis as part of their mechanistic paths to successful bio-catalysis, (a) triose phosphate isomerase (TIM), (b) lysozyme, (c) RNAse A. In all cases substrates are shown in red. Lone pair donor amino acid residues are general bases, lone pair acceptor amino acid residues are general acids. Note that pK (a commonly used term) is the equivalent of p/f/ or pK (as written in this text book) as appropriate for an acidic or basic functional group.

M. Karplus, J. D. Evenseck, D. Joseph, P. A. Bash, and M. J. Field, Faraday Discussions, 93, 239 (1992). Simulation Analysis of Triose Phosphate Isomerase—Conformational Transition and Catalysis. 

Another concerted general acid-base catalysis is illustrated by triose phosphate isomerase, an enzyme involved in glycolysis. Here, the concerted action involves the carboxylate anion of a glutamic acid residue as a general base with a general acid which has not yet been identified ... 

Glucose-6-P is then isomerized by phosphohexose isomerase to fructose-6-P (making up 30% of the equilibrium mixture). Another kinase phosphorylates the 1-position and the resulting fructose diphosphate is cleaved in an equilibrium reaction to two trioses, namely dihydroxyacetone phosphate (C-1 to C-3) and glyceral-dehyde phosphate (C-4 to C-6). The equilibrium mixture is composed of 89% hexose and 11% triose (under the conditions of Meyerhof s measurements) condensation, therefore, is the preferred (= exergonic) reaction. The reaction is analogous to the aldol condensation described in organic chemistry (Chapt. 1-2, XV-5). Catalysis of the reverse reaction by the enzyme aldolase is explained by the fact that enzymes always catalyze up to the equilibrium. ... 

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