Purification and Properties of Phenylalanine Ammonia-Lyase from Strawberry Fruit and its Synthesis during Ripening

Abstract

Listen

Translate article

Summary Phenylalanine ammonia-lyase (PAL) extracts from ripe strawberry fruit give a linear Eadie-Hofstee plot and show a single predominant isozyme of pI 5.45. The enzyme has a native molecular weight of approximately 266,000. On sodium dodecyl sulphate polyacrylamide gel electrophoresis purified preparations yield a single band of Mr 72,000 which reacts with bean PAL antiserum on a Western blot, but does not react with Concanavalin A. Labelling with 35 S-methionine in vivo shows that protein synthesis is occurring both in unripe and in ripening strawberry fruit over the period when PAL activity is developing. The bean PAL antiserum was used to prepare immunoprecipitates from 35 S-methionine labelled extracts of strawberry fruit of different maturities. The appearance of a band of Mr 72,000 in immune but not non-immune immunoprecipitates from pink and red fruit coincides with loss of PAL activity from the corresponding supernatants. This suggests that the increase in PAL activity in ripening strawberry fruit is due to de novo synthesis of the enzyme.