Proteolytic activity associated with the cell wall

As extracellular soluble proteins decreased during hypocotyl elongation significantchanges in polypeptide pattern in the same protein fraction were observed,suggesting the presence of cell-wall associated protease(s) Extracellular fluid(EF), containing water-soluble and cell wall-ionically bound proteins, was extractedfrom etiolated bean hypocotyls, and protease activity was measured at differentpHs. Significant endopeptidase activity was observed at acid pH, becoming maximalat pH 4 5 Moreover, an endopeptidase (EP) with similar pH optimum, wasisolated from EF by affinity chromatography on haemoglobin-agarose gel Theisolated enzyme showed high thermal and temporal stability and dependence onmetal cofactors, EP seems to be a monomeric enzyme with apparent mol massof 52 kDa and it could hydrolyze several extracellular soluble polypeptides AcidicEP activity increased during hypocotyl growth, reaching its highest value duringthe exponential phase of the elongation, and then decreased It is proposed thatthe EP could be involved in the regulation of cell wall elongation.

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