Food Biochemistry and Food Processing

7

Enzyme Activities

†

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

155

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

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, chim-

panzees, 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 1100 BC), 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

220 BC) in China, a spicy paste or sauce made from

fermentation of soybean and/or wheat was men-

tioned. It is now called soybean sauce.

Although people applied fermentation techniques

and observed the changes from raw materials to spe-

cial products, they did not realize the mechanisms

*Corresponding author.
†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 Bioengineering, University of Hawaii at
Manoa, Honolulu, Hawaii, USA.

Food Biochemistry and Food Processing

Edited by Y. H. Hui

Copyright © 2006 by Blackwell Publishing