Characterization of a cDNA encoding cottonseed catalase.

Area of Science:

• Plant Molecular Biology
• Enzymology
• Biochemistry

Background:

• Catalases are crucial enzymes involved in cellular defense against oxidative stress.
• Understanding plant catalase structure and function is vital for agricultural and biotechnological applications.
• Previous studies have characterized catalases from various plant species, but cotton catalase remains less explored.

Purpose of the Study:

• To isolate and characterize the cDNA encoding cotton seed catalase.
• To determine the amino acid sequence and compare it with other known catalases.
• To identify conserved regions important for catalytic activity and structural integrity.

Main Methods:

• Construction of a lambda gt11 cDNA library from poly(A) RNA of 24-hour-old cotton cotyledons.
• Isolation and sequencing of a 1.7 kb cDNA clone encoding catalase.
• Bioinformatic analysis including amino acid sequence comparison and molecular mass calculation.

Main Results:

• A full-length catalase peptide of 492 amino acid residues was encoded by the isolated cDNA.
• The deduced molecular mass (56,800 Da) closely matched the purified enzyme's mass (57,000 Da).
• Cotton catalase exhibited 85% amino acid sequence identity to maize CAT 1, with highly conserved catalytic and structural regions compared to other plant and yeast catalases.

Conclusions:

• The cotton catalase cDNA encodes a functional enzyme with high similarity to other plant catalases.
• Conserved amino acid residues and regions underscore the fundamental importance of these for catalase activity and structure.
• The C-terminus lacks a canonical peroxisomal targeting signal, suggesting alternative import mechanisms or localization.