Involved in the biosynthesis of undecylprodigiosin (PubMed:11514230, PubMed:11880032). Catalyzes the desaturation of the L-prolyl-[prolyl-carrier protein] to yield 1H-pyrrole-2-carbonyl-[prolyl-carrier protein] (PubMed:11880032). H(+) + L-prolyl-[peptidyl-carrier protein] + 2 oxidized [electron-transfer flavoprotein] = (1H-pyrrole-2-carbonyl)-[peptidyl-carrier protein] + 2 reduced [electron-transfer flavoprotein] Belongs to the acyl-CoA dehydrogenase family.