DEVELOPMENTAL-CHANGES IN CARBOHYDRATE CONCENTRATION AND ACTIVITIES OF SUCROSE METABOLIZING ENZYMES IN FRUITS OF 2 CAPSICUM-ANNUUM-L GENOTYPES

Recently it was reported that hexose sugars accumulate in pepper (Capsicum annuum) fruit during ripening as a result of increased acid invertase (EC 3.2.1.26) activity. In this study, fruit of two pepper genotypes which differ in size, shape and carbohydrate concentration were evaluated during growth and development. Carbohydrate concentrations and sucrose metabolizing enzyme activities were measured. Starch and sucrose concentration increased midway through development and declined during fruit ripening. The increase in sucrose concentration was seemingly unrelated to activity of sucrose-phosphate synthase (SPS) (EC 2.4.1.14). As sucrose and starch concentrations declined during ripening, hexose sugar concentration increased. This change in carbohydrate composition was associated with increased acid and neutral invertase activity. Overall trends in carbohydrate pools and enzyme activities were similar between the two genotypes. However, the smaller jalapeno-shaped pepper had much higher carbohydrate concentrations and enzyme activities than the bell pepper. The most striking differences between the two genotypes were a very high concentration of hexose sugars (>90 mg/g fresh wt.) and the extent to which activity of acid and neutral invertases increased during the final stages of ripening in the jalapeno-shaped pepper compared to the bell-shaped pepper. Thus, there may be an association between increased invertase activity and the accumulation of hexose sugars in pepper fruit during ripening.