Isozymes Adaptation

Fig. 3 Elaboration of the DCL of inhibitors inhibition constants K and the amplification of the constitutional dynamic library (CDL) against catalytically active human hCA I and hCA II cytosolic isozymes (adapted from [66])...

Phospholipases. Figure 2 Representation ofthe domains in the major isozymes of phospholipase C (adapted from [2]). 

Although mice with mutations in the myosin-6, -7a, and 15a genes are deaf, these isozymes apparently mediate essential hair-cell functions besides adaptation. Myosin-7a may play an important role in bundle integrity, as mice and fish with no functional myosin-7a protein have highly disheveled bundles. 

Fig. i Constitutional dynamic chemistry applied to bovine carbonic anhydrase bCA II isozyme and elaboration of constitutional dynamic library (CDL). Precursor amines a-d and aldehydes 1-3 and resulting components of the combinatorial library Ia-c-3a-c. HPLC traces of the final reaction mixtures showing amplification of 3c and 3d (adapted from [49])... 

In the context of enzymes, various mechanisms allow adaptation to fluctuating environmental conditions. Most importantly, mechanisms for transcriptional control and allosteric regulation have evolved to modulate enzyme expression and activities and the consequent fluxes through metabolic pathways in response to environmental perturbations. Another mechanism for adaptation to variable environmental conditions is evolution of isozymes that catalyze a common reaction, but function optimally under different conditions. 

Evans SA Shore JD (1980) The role of zinc-bound water in liver alcohol dehydrogenase catalysis. J Biol Chem 255 1509-1514 Eventoff W, Rossmann MG, Taylor SS, Torff H-J, Meyer H, Keil W, Kiltz H-H (1977) Structural adaptations of lactate dehydrogenase isozymes. Proc Natl Acad Sci USA 74 2677-2681 Fisher HF, Conn EE, Vennesland B, Westheimer FH (1953) The enzymatic transfer of hydrogen I. The reaction catalyzed by alcohol... 

Although the enzymatic machinery for P-enolpyruvate carboxylation in the nonautotrophic pathway, C3-photosynthesis, C4-photosynthesis, and CAM is similar, the enzymes are sufficiently different to be classed as isozymes, and hence, we assume evolutionary pressures have resulted in a common theme (PEP carboxylation) being modified for similar, but functionally different adaptive roles (see Chap. 4). 

Eventoff, W., Rossmann, M. G., Taylor, S. S., Torff, H-S., Meyer, H., Keil, W., and Kiltz, H-H., 1977, Structural adaptations of lactate dehydrogenase isozymes, Proc. Natl. 

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