Purification and properties of an aminopeptidase from buckwheat seed.

An aminopeptidase was purified from buckwheat seed by using affinity chromatography, ionexchange chromatography and chromatofocusing.The enzyme had a molecular weight of 37,000 as determined by gel filtration.The aminopeptidase activity, determined with L-leucine-p-nitroanilide (Leu-PNA) as the substrate, exhibited a pH optimum of 7.2.The Kmvalue for Leu-PNAwas 140 fiM.The preferred substrates were L-leucine-/?-naphtylamide and Leu-PNA, although there was also high activity against L-leucyl-L-alanine and L-leucinamide.Thiol antagonists were found to be potent inhibitors against the enzyme.The enzymeexhibited less or no sensitivity to the endogeneous proteinase inhibitors, benzamidine and TPCK.