Abstract
Acetyl‐CoA carboxylase is known to be the site of action of two groups of grass‐selective herbicides: the aryloxyphenoxypropionates and the cyclo‐hexanediones. This enzyme was extracted from maize leaves, and a novel, highly sensitive assay system developed, utilising measurement of phosphate to estimate enzyme activity. This assay system was verified by using inhibition by fluazifop and avidin to compare it with the more widely used 14C assay. K m values for acetyl‐CoA were measured, and inhibition kinetics investigated.