Back to Tertiary Index . . . 6th Apr'95
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Segregation of functions

Several multi-domain enzymes show segregation of their functions, such as substrate binding and catalysis, to separate domains. The NAD (nicotinaminde adenine dinucleotide) dependent dehydrogenases, such as lactate dehydrogenase, are classical examples of this. These enzymes contain a dinucleotide binding domain, with a alpha/beta doubly-wound topology known as the Rossman fold, and a substrate binding domain.

Phosphofructokinase is another case where different functions are seen to be carried by different domains. One subunit of phosphofructokinase consists of two domains one of which carries the active site and the other which carries the allosteric effector site where both activators and inhibitors bind. It is important to note that the allosteric effect is transmitted through changes in the inter-subunit interfaces and not inter-domain interfaces.

A few examples:

1. substrate-binding and NAD-binding domains of D- glyceraldehyde-3-phosphate dehydrogenase.

2. catalytic and effector domains of one subunit of phosphofructokinase

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