A NEW ACYL-COA SYNTHETASE, LOCATED IN HIGHER-PLANT CYTOSOL

A novel soluble acyl-CoA synthetase (pimeloyl-CoA synthetase; EC 6.2.1.14) distinct from the known membrane bound acyl-CoA synthetases has been characterized for the first time in higher plant cells. This enzyme is the first one involved in the biosynthesis pathway of biotin in higher plant cells and catalyzes the activation of pimelic acid (COOH-(CH2)(5)-COOH) to pimeloyl-CoA. The bulk of activity was shown to be exclusively associated with the cytosolic fraction at a specific activity of 0.3 nmol min(-1) mg cytosolic protein(-1). Pimelic acid as a substrate is not recognized by the known chloroplastic acetyl-CoA synthetase. However, in the peroxisomes pimelic acid is also activated to pimeloyl-CoA by the acyl-CoA synthetase. The pimeloyl-CoA thus formed is subsequently degraded to acetyl-CoA and malonyl-CoA.