Involved in the biosynthesis of a unique class of isonitrile lipopeptides (INLPs) that seem to function as virulence factors in M.tuberculosis and to play a role in metal acquisition. Catalyzes the conversion of (3R)-3-[(carboxymethyl)amino]fatty acids to (3R)-3-isocyanyl-fatty acids through an oxidative decarboxylation mechanism, thereby generating the isonitrile group of INLPs 