An enzymatic fraction (PPE) obtained by selective precipitation from a
pea seedling extract was
shown to catalyze putrescine incorporation. In order to elucidate
the type of enzyme, transglutaminases or diamine oxidases (DAO), involved in this activity, the ability
of this PPE fraction to catalyze
their characteristic reactions, amine binding, deamidation, protein
cross-linking, and oxidation was
investigated. The use of specific enzyme inhibitors pointed out
that only DAO was present in the
extract and should be involved in the protein cross-linking reactions.
This reaction was only
catalyzed in the presence of diamines, especially putrescine and
cadaverine, or polyamine like
spermidine.
Keywords: Guinea pig liver transglutaminase; pea seedling diamine oxidase;
amine binding; cross-linking; deamidation; Pisum sativum
The activity of a purified pea diamine oxidase (DAO) was compared to
that of a pea seedling
enzymatic extract (PPE). It has been shown that DAO is able to
catalyze as PPE the binding of
amine to proteins as well as protein cross-linking reactions, but only
if diamines and Cu2+ ions are
both available in the medium. We proposed a mechanism in two steps
for this reaction: first, an
enzymatic step which induces the formation of an aldehyde resulting
from the enzymatic oxidation
of the diamine by DAO and, second, a chemical step catalyzed by
Cu2+ which corresponds to the
addition of nucleophilic amino acid side chain with the carbonyl group
of the aldehyde. This last
chemical reaction may lead in a first stage to the amine binding or in
a second stage to protein
cross-linking.
Keywords: Pea seedling diamine oxidase; amine binding; cross-linking;
deamidation; Pisum
sativum
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