Studies on the Plant Methylcrotonyl-CoA Carboxylase 1

Abstract

Summary In our research on the presence of biotin-containing carboxylases in plants we found, in addition to acetyl-CoA carboxylase (ACC), the carboxylation of propionyl-CoA (PCC-activity) and methylcrotonylCoA (MCC-activity) in protein preparations from maize, oat, barley, pea and lentil. Whether the PCCactivity originates from a distinct, separate enzyme or represents a side-activity of the ACC is not yet clear. The carboxylation of methylcrotonyl-CoA is clearly catalyzed by a new biotin enzyme, the methylcrotonyl-CoA carboxylase (MCC), which can be inhibited by avidin. It is not present in isolated chloroplasts, but seems to be a component of plant mitochondria. In contrast to ACC and PCC, the MCC of barley and maize is not inhibited by two herbicide groups, known to be strong inhibitors of the ACC from grasses. The activity of ACC and MCC from maize exhibit a quite different developmental pattern: ACC is found in young leaf tissue, whereas MCC shows up only in older tissue. The MCC from barley was purified 60-fold using different HPLC columns.