Enzyme Reaction Lab Report

KINETICS OF MULTISUBSTRATE REACTIONS

Introduction

Enzyme kinetics is the study of rate of biochemical reactions that are catalyzed by enzymes. In enzyme kinetics, the reaction rate is measured and the their effect is measured or investigated. Studying an enzyme kinetics in this way we can check the catalytic activity of enzyme, its major role in metabolism, and how its activity is determined. Enzymes are protein in nature and binds to substrates. These substrate molecules bind to active site of enzyme and changed into products through a number of steps known as enzymatic reactions. The general reaction for this mechanism is as follows: E + S ⇄ ES ⇄ ES ⇄ EP ⇄ E + P Many of the most intensively studied

All substrates, if not specifically stated, are designated as A,B,C and D. All products are designated as P,Q,R. Different forms of enzymes are represented by E,F,G. E is the form of the enzyme that is free or at least most nearly free of any form of the substrates or products. Kineticists recognize two general mechanism for multisubstrate reactions: Sequential Mechanisms Non Sequential Mechnisms

1. Sequential Mechanisms

The first important type of Bi-Bi reaction is known as sequential, which means that all substrates must add to the enzyme before any reaction takes place. It is divided two more mechanisms: Ordered Mechanism Random

acetyl CoA + ATP + HCO-3 □(⇔┴( BIOTIN ) )Malonyl CoA +ADP+ Pi

This is designated as Bi, Bi , Uni, Uni, ping pong mechanism because first two substrates add to the enzyme, then two products are released, then another substrate adds and the final product is released.

Acetly coa carboxylase catalyzes coupled reaction. That is it mediates the energetically unfavourable formation of a carbon-carbon bond by coupling the reaction to the structurally unrelated but energetically favorable hydrolysis reaction of ATP to ADP and inorganic phosphate.

To determine the order of the additions of substrates and products in a multisubstrate, multiproduct enzyme system generally requires a variety of experiments, including detailed kinetic analysis of the reaction rates with all but one of the substrates and products set at fixed concentration while one substrate or product is varied. The equilibrium constant for the binding of substrates and cofactors alone and in the presence of others, product inhibition kinetics and other measurement all can contribute to determining the type of the