Question

Condsider five conditions of some enzyme(s) with the following Lineweaver-Burk equations.

A) y = 1x + 0.25

B) y = 0.25x + 0.25

C) y = 1x + 1

D) y= 1x + 4

E) y= 0.25x + 1

i) Which set of conditions demonstrates the enzyme that is least able to form the ES complex easily?

v) Which pair of sets of conditions would represent an enzyme with and without a competitive inhibitor?

vi) Which pair of sets of conditions would represent an enzyme with an without a noncompetitive inhibitor?

vii) Which pair of sets of conditions would represent an enzyme in the presence of an allosteric activator and in the presence of an allosteric inhibitor?

viii) Which set of conditions demonstrates the enzyme with the lowest k1?

ix) Which set of conditions shows an enzyme with equal values for Vmax and Km?

x) Which set of conditions shows an enzyme with a specific constant of 1?

Answer 1

The enzymatic reaction can be written as

This is a two-step process, in which the substrate S forms an intermediate ES with enzyme E which in turn produces the product P.

The Lineweaver equations can be generally written as

where

There are three types of inhibtors namely competeitive, uncompetitive and non-competitive.

Case 1: Competitive Inhibitor

Here

In the case of competitive inhibitor the Lineweaver equations can be written as

for no inhibitor and

with inhibitor

This means intercept remains same and slope increases with increase in competitive inhibitor concentration

Case 2: Uncompetitive Inhibitor

, Which cannot react further.

In the case of competitive inhibitor the Lineweaver equations can be written as

for no invibitor and

  with uncompetitive inhibitor

This means slope remains same and intercept increases with uncompetitive inhibitor concentration

Case 3: Non-Competitive Inhibitor

Here

Both E and ES cannot react to form product,

In the case of non-competitive inhibitor the Lineweaver equations can be written as

for no inhibitor and

  with non-competitive inhibitor

This means slope and intercept increases with non-competitive inhibitor concentration

From the above discussions the the questions can be answered

1. The that is least able to form ES is in the case of non-competitive inhibitor and the conditions are

A and E; B and C; B and D

V. A and B; C and E

VI. A and E; B and C; B and D