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Calcium activation of peanut lipoxygenase
Author(s) -
Nelson M. S.,
Pattee H. E.,
Singleton J. A.
Publication year - 1977
Publication title -
lipids
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.601
H-Index - 120
eISSN - 1558-9307
pISSN - 0024-4201
DOI - 10.1007/bf02533626
Subject(s) - chemistry , lipoxygenase , calcium , biochemistry , enzyme , organic chemistry
Abstract Peanut lipoxygenase isozyme 1 (pH optimum, 8.3) was strongly activated by 0.5–1.0 mM Ca ++ , and the rate of activation was maximum when the ratio of substrate to Ca ++ was ca. 2∶1. Peanut lipoxygenase isozymes 2 and 3 (pH optima, 6.2) were activated by calcium but did not have an optimum level of activity. Calcium differentially activated peanut lipoxygenase causing the rate of pentane production to increase much more rapidly than the rate of oxygen consumed by the enzyme reaction. At pH 6.2, in the absence of calcium, the percentages of the hydroperoxide isomers produced by peanut lipoxygenase were 74.9% 13‐hydroperoxy cis ‐9, trans ‐11‐octadecadienoic acid (13 LOOH cis‐trans ), 2.6% 13‐hydroperoxy trans ‐9, trans ‐11‐octadecadienoic acid (13 LOOH trans‐trans ) and 22.5% 9‐hydroperoxy 10, 12‐octadecadienoic acid (9 LOOH). The presence of 1 mM Ca ++ at pH 6.2 did not significantly affect the percentage distribution of the hydroperoxides produced. However, at pH 8.3, the percentage distribution of hydroperoxides produced was 45.2% 13 LOOH cis‐trans , 10.9% 13 LOOH trans‐trans and 43.9% 9 LOOH in the absence of Ca ++ and 57.0% 13 LOOH cis‐trans , 8.0% 13 LOOH trans‐trans and 35.0% 9 LOOH in the presence of 1 mM Ca ++ .