Planta

, Volume 179, Issue 3, pp 316–322 | Cite as

The role of cysteine proteinase and carboxypeptidase in the breakdown of storage proteins in buckwheat seeds

  • Y. E. Dunaevsky
  • M. A. Belozersky
Article

Abstract

Two proteolytic enzymes, a cysteine proteinase and a carboxypeptidase, responsible for breakdown of the main storage protein, 13S globulin, were purified from buckwheat seedlings (Fagopyrum esculentum Moench) by (NH4)2SO4 fractionation, gel-filtration on Sephadex G-150, ionexchange chromatography on DEAE-Toyopearl 650 M and chromatofocusing. The cysteine proteinase was purified 74-fold. It has a pH optimum of 5.5, a pI of 4.5 and an apparent molecular mass (Mr) of 71000. The carboxypeptidase was purified 128-fold. It has a pH optimum of 5.3, a pI of 5.8 and a Mr of 78500. Cysteine proteinase hydrolyzed the modified 13S globulin only if the reaction products were eliminated from the incubation mixture by dialysis. Storage protein degradation by the proteinase increased in the presence of carboxypeptidase. We suggest that the two enzymes complete the digestion of 13S globulin after its preliminary hydrolysis by the earlier described enzyme, metalloproteinase, present in dry buckwheat seeds.

Key words

Carboxypeptidase Cysteine proteinase Proteolysis Fagopyrum Storage protein 

Abbreviations

BSA

bovine serum albumin

DEAE

diethylaminoethyl

Mr

apparent molecular mass

PAGE

polyacrylamide gel electrophoresis

SDS

sodium dodecyl sulfate

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Copyright information

© Springer-Verlag 1989

Authors and Affiliations

  • Y. E. Dunaevsky
    • 1
  • M. A. Belozersky
    • 1
  1. 1.A.N. Belozersky Laboratory of Molecular Biology and Bioorganic ChemistryMoscow State UniversityMoscowUSSR

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