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Related Experiment Videos

Subterminal polygalacturonase, a nonmacerating enzyme, attacks pectate from the reducing end.

J H McClendon1

  • 1School of Life Sciences, University of Nebraska, Lincoln, Nebraska 68588.

Plant Physiology
|January 1, 1979
PubMed
Summary

Subterminal polygalacturonase from Aspergillus acts at the reducing end of pectate, unlike endo-polygalacturonase from Saccharomyces fragilis. This enzyme activity was confirmed by tracking labeled substrates and hydrolysis products.

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Area of Science:

  • Enzymology
  • Plant Biochemistry
  • Microbial Biochemistry

Background:

  • Polygalacturonases are key enzymes in pectin degradation.
  • Understanding enzyme action mechanisms is crucial for biotechnological applications.

Purpose of the Study:

  • To elucidate the mode of action of subterminal polygalacturonase from Aspergillus on pectate.
  • To compare its activity with endo-polygalacturonase from Saccharomyces fragilis.

Main Methods:

  • Enzymatic hydrolysis of modified pectate substrates (tritium-labeled reducing end, unsaturated non-reducing end).
  • Separation of hydrolysis products using gel filtration chromatography.
  • Quantification of sugar residues, tritium label, and UV absorption.

Main Results:

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  • Subterminal polygalacturonase rapidly released tritium-labeled oligomers, indicating action initiated at the reducing end.
  • Enzyme activity at the reducing end was significantly faster than at the non-reducing end or on unlabeled oligomers.
  • Accumulation and subsequent hydrolysis of unsaturated pentamers and hexamers further supported reducing-end-initiated activity.

Conclusions:

  • Subterminal polygalacturonase from Aspergillus exhibits a distinct reducing-end-specific mode of action on pectate.
  • This contrasts with the endo-acting mechanism of endo-polygalacturonase from Saccharomyces fragilis.
  • The findings provide insights into the substrate specificity and catalytic mechanism of fungal polygalacturonases.