Enzymes play a key role in plant disease development by breaking down plant substances into molecules that pathogens can absorb and use for growth. Different types of enzymes produced by pathogens include cutinases, pectinases, cellulases, hemicellulases, ligninases, proteases, amylases, and lipases. These enzymes degrade the cuticle, cell walls, proteins, starch, lipids, and other plant tissues, which the pathogens then utilize as nutrients.

1. Role of enzymes in pathogenesis
N. H. SHANKAR REDDY
2nd, Ph.D., Plant Pathology
Annamalai University

2. • Enzymes – Enzymes are large protein molecules (2-100 mµ
in diameter) which act as a catalyst to bring a specific
chemical reaction in living cells (where it converts specific
set of reactants to specific products)
• A cell contains several million enzymes, which belongs to
different kinds of enzymes.

3. • Enzymes secreted by microorganism play a key role in
disease development. These break down plant substances
into smaller molecules which pathogen easily absorb and
utilize for its growth and energy.
• Different types of enzyme are reproduced by pathogen are

4. Cutinases
• Cutinases which degrade cutin,
is the main component of the
cuticle, is known to produce by
many fungi and bacteria.
• Eg - Puccinia hordei

5. Pectinases
• Degrade pectic substances
which is chief component of
middle lamella of plant cells.
• Eg - Phytophthora, Pythium

6. Cellulases
• Produced by several plant
pathogenic fungi, bacteria and
nematodes, which plays a major
role in softening
• Eg - Fusarium

7. Hemicellulases
• Which breakdown
hemicelluloses, are complex
mixture of polysaccharides and
a major component of primary
cell wall
• Eg - Sclerotinia sclerotiorum

8. Ligninases
• Breakdown most resistant
component to enzymatic
degradation, lignin
• Eg - Brown rot fungi, white
rot fungi, Xylaria
polymorpha

9. Proteases
• Which degrade proteins
• The degradation of host
proteins by proteolytic enzymes
secreted by pathogens affects
the organization and function of
the host cell.
• Eg - Helminthosporium oryzae

10. Amylases
• Which breakdown starch
into glucose and utilised by
the pathogen
• Fatty Acid is directly
utilized by the pathogen.
• Eg – Many fungi, bacteria,
and nematodes

11. Lipases
• Which breakdown lipids
(phospholipids, glycolipids). Several
fungi, bacteria & nematodes.
• Eg - Sclerotium rolfsii, Botrytis
cinerea