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Invertase and sucrose synthase activity, carbohydrate status and endogenous IAA levels during Citrus leaf development
Author(s) -
Schaffer Arthur A.,
Sagee Oded,
Goldschmidt Eliezer E.,
Goren Raphael
Publication year - 1987
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1987.tb01959.x
Subject(s) - invertase , sucrose , sucrose synthase , sucrose phosphate synthase , sugar , chemistry , enzyme , enzyme assay , biochemistry , carbohydrate
Levels of activity of the sucrose catabolizing enzymes, acid invertase (EC 3.2.1.26) and sucrose synthase (EC 2.4.1.13), were measured during development of new leaves of Citrus sinensis (L.) Osbeck cv. Shamouti. Soluble acid invertase showed a peak activity of 32 nkat (g fresh weight) −1 at ca 60% of full leaf expansion and rapidly declined toward and after full expansion. There was no concomitant increase in an insoluble form of the enzyme. Sucrose synthase activity, measured in the synthesis direction, declined from 33% of full leaf expansion [10 nkat (g fresh weight) −1 ] 10, and following, full expansion. Highest sucrose synthase activity, measured in the cleavage direction, was 6 nkat (g fresh weight) −1 and showed little change during development. Acid invertase has a K m of 5 m M for sucrose, while sucrose synthase had a K m of 118 m M for sucrose. Changes in acid invertase activity correlated with changes in the reducing sugar:sucrose ratio. These results suggest that soluble acid invertase activity is the primary enzyme responsible for sucrose catabolism in the expanding Citrus leaf. Changes in leaf expansion rate and invertase activity did not correlate positively with changes in endogenous free IAA level, as determined by enzyme linked immunoassay.