Question

Enzymes (or their production) are often regulated in a negative or positive way, depending on whether they are related to anabolic (building) or catabolic (breaking down) reactions. Please describe, in your own words, why excess of products might inhibit enzymatic activity for anabolic reactions but why excess of reactants might stimulate enzymatic activity for catabolic reactions. This question is pretty complex, so take your time to develop your thoughts prior to typing your answer. The best answers should incorporate aspects of bioenergetics, genetic expression, and cell biology.

Answer 1

Genetic expression aspect: production of enzymes or activation of enzymes depends upon the concentration of the substrates. For example when high substrate concentration is available then more amount of enzymes are produced or activated for more catalytic reaction. In this we can see the expression of genes which are involved in the production of enzymes in various metabolic reactions.

Gene expression for enzyme production or activation can be done by following conditions:

1. when high substrate concentration occurs then it activates various signalling proteins which further move to nucleus and stimulate the gene expression for the production of enzyme. Hence we can say high amount of substrate induce high amount of enzyme production. As the amount of substrate reduces and various other proteins inhibits the gene expression and reduces the enzyme production.

We can say amount of substrate and amount of product controls the regulation and quantity of enzymes buy regulation of gene expression. This regulation depends upon the multiple cell signalling Pathways which have rules of various different proteins known is signalling proteins.

Example : various cell division enzymes and polymerases.

In cells enzymes are present but these are present in the inactive form when the substrate concentration is available this inactive form is converted into active form.

For example Digestive enzymes: these are present in an inactive form and as the food comes they secreated out from cells and converted into active form for the catalysis of reactions. Hence the product concentration increases and substrate concentration decreases, secretion of these enzymes also reduces and controls the enzymatic reaction. Pepesinogen converted into pepsin.

Trypsinogen converted into trypsin.

In the bioenergetics aspect The breakdown of substrate requires more energy and then this energy is provided by ATP in lot of reactions. When the amount of ATP is less than the reaction for background is not occurs. Excess of product leads to reduction of ATP which is not utilised by the enzymatic conversion reaction and leads to reduction in production of products.

Gibs free enenegry. Concentration of NADH and NADP ATP