Biomedical Engineering Reference
In-Depth Information
C
HAPTER
3
Induction and Repression of
Carbohydrate Degrading Enzymes
in Fungi with Special Reference
to their Coding Genes
Pauline Walsh*, Alan Hernon and Anthonia O'Donovan
Abstract
The exact mechanism by which large insoluble carbohydrates induce the expres-
sion of the arsenal of enzymes required for their complete hydrolysis has eluded
scientists for decades. Several scientists have proposed confl icting hypotheses
to solve this puzzle but none have provided a defi nitive answer. This chapter
describes the various proposed mechanisms of plant cell wall degrading enzyme
induction and gives a brief overview of the key transcription factors regulating
them. The biotechnological importance of these enzymes has grown rapidly in
the last decade as we turn to plant material to provide energy, platform chemicals
and nutraceuticals. The enzyme production industry would benefi t greatly from
a complete understanding of the induction mechanism.
INTRODUCTION
The production of complete plant cell wall degrading enzyme systems by
fungi requires an enormous amount of energy and thus places a signifi cant
metabolic pressure on a fungus. Consequently, fungi have developed
complex multi-component regulatory systems that repress expression
of cell wall hydrolases in the presence of simple carbon sources, such
as glucose and induce expression of a more complete enzyme system
in the presence of more complex carbon sources, such as cellulose. The
