Food Biochemistry and Food Processing (2 edition)

BLBS102-c08 BLBS102-Simpson March 21, 2012 12:8 Trim: 276mm X 219mm Printer Name: Yet to Come

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Enzyme Activities

D. J. H. Shyu, J. T. C. Tzen, and C. L. Jeang

Introduction

Features of Enzymes

Most of the Enzymes are Proteins

Chemical Composition of Enzymes

Enzymes are Specific

Enzymes are Regulated

Enzymes are Powerful Catalysts

Enzymes and Activation Energy

Enzymes Lower the Activation Energy

How Does an Enzyme work?

Enzyme Kinetics and Mechanism

Regulatory Enzymes

Feedback Inhibition

Noncompetitive Inhibition

Competitive Inhibition

Enzyme Kinetics

Data Presentation

Untransformed Graphics

Lineweaver–Burk Plots

Eadie–Hofstee Plots

Hanes–Wolff Plots

Eisenthal–Cornish-Bowden Plots (the Direct Linear

Plots)

Hill Plot

Factors Affecting Enzyme Activity

Enzyme, Substrate, and Cofactor Concentrations

Effects of pH

Effects of Temperature

Methods Used in Enzyme Assays

General Considerations

Types of Assay Methods

Detection Methods

This manuscript was reviewed by Dr. Hsien-Yi Sung, Department of Biochemical

Science and Technology, National Taiwan University, Taipei, Taiwan, Republic

of China, and Dr. Wai-Kit Nip, Department of Molecular Biosciences and Bio-

engineering, University of Hawaii at Manoa, Honolulu, Hawaii, USA.

Spectrophotometric Methods

Spectrofluorometric Methods

Radiometric Methods

Chromatographic Methods

Electrophoretic Methods

Other Methods

Selection of an Appropriate Substrate

Unit of Enzyme Activity

References

INTRODUCTION

Long before human history, our ancestors, chimpanzees, might

have already experienced the mild drunk feeling of drinking

wine when they ate the fermented fruits that contained small

amounts of alcohol. Archaeologists have also found some sculp-

tured signs on 8000-year-old plates describing the beer-making

processes. Chinese historians wrote about the lavish life of Tsou,

a tyrant of Shang dynasty (around 1100bc), who lived in a castle

with wine-storing pools. All these indicated that people grasped

the wine fermentation technique thousands of years ago. In the

Chin dynasty (around 220bc) China, a spicy paste or sauce made

from fermentation of soybean and/or wheat was mentioned. It is

now called soybean sauce.

Although people applied fermentation techniques and ob-

served the changes from raw materials to special products, they

did not realize the mechanisms that caused the changes. This

mystery was uncovered by the development of biological sci-

ences. Louis Pasteur claimed the existence and function of or-

ganisms that were responsible for the changes. In the same era,

Justus Liebig observed the digestion of meat with pepsin, a

substance found in stomach fluid, and proposed that a whole

organism is not necessary for the process of fermentation.

In 1878, Kuhne was the first person to solve the conflict by in-

troducing the word “enzyme,” which means “in yeast” in Greek.

Food Biochemistry and Food Processing, Second Edition. Edited by Benjamin K. Simpson, Leo M.L. Nollet, Fidel Toldr ́a, Soottawat Benjakul, Gopinadhan Paliyath and Y.H. Hui.

©C2012 John Wiley & Sons, Inc. Published 2012 by John Wiley & Sons, Inc.

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