Characterisation of leucyl aminopeptidase from Solanum tuberosum tuber

Potato juice (a waste product from the starch industry) is a potential source of novel enzymes for food applications. For use in the production and improvement of food protein hydrolysates, commercially available exopeptidases, predominantly aminopeptidases, are recommended. The present study was performed to explore possible biotechnological interest of leucyl aminopeptidase (LAP) activity in the potato tuber. The LAP from potato tuber was purified and characterised. Specific LAP activity was increased 200-fold by purification of the crude extract. The purified enzyme had a pH optimum of 9.0 and temperature optimum of 45 °C. LAP hydrolysed leucine-, alanine- and lysine-p-nitroanilide to a similar degree. The most efficient inhibitor was 1,10-phenanthroline. Almost all divalent cations tested inhibited the enzyme activity, while Co2+ stimulated LAP activity by over 100%. The purified LAP had a molecular weight of 90 kDa with an isoelectric point of 5.45. Sodium dodecylsulfate-polyacrylamide gel electrophoresis revealed one band of 48 kDa.