Metabolism of l-carnitine in bacteria. Enzymes involved are GBB dioxygenase (1), γ-butyrobetainyl-CoA synthetase (2), γ-butyrobetainyl-CoA dehydrogenase (3), crotonobetainyl-CoA hydratase (4), l-carnitinyl-CoA thiolase (5), l-carnitine dehydrogenase (6), dehydrocarnitine cleavage enzyme (BKACE) (7), and betainyl-CoA thiolase (8).