Fat Metabolism in Higher Plants

Abstract

The conversion of malonyl coenzyme A to long chain fatty acids has been studied in enzyme systems from various tissues (l-7). Attempts to purify the enzymes involved in this conversion revealed an important difference between these systems. Thus the highly purified synthetase from yeast (8, 9) and from liver (10, 11) behaves as a single complex; its fractionation has not yet been accomplished. However, extracts of Clostridium kluyveri and Escherichia coli can be resolved into several components which on combination catalyze the synthesis of fatty acids (7, 12-16). One of these components has the rather unusual property of being relatively stable to heat and dilute hydrochloric acid (7, 12, 13). Acetyl and malonyl moieties can be transferred from their coenzyme A derivatives to this protein. The acyl complexes are then condensed by suitable enzymes to form acetoacetyl-enzyme, which is subsequently converted to butyryl-enzyme (15-19). These findings support the scheme proposed earlier for the synthetase from yeast (8) .I Extracts from avocado mesocarp contain, in addition to the previously studied particulate system (5,20), a soluble enzymatic system, which converts malonyl coenzyme A to saturated long chain fat’ty acids (21). This soluble enzyme has as one of its components a heat-stable protein and therefore resembles the bacterial systems. Some of the data discussed here have already been reported elsewhere (22).