Converts carnitine to trimethylamine and malic semialdehyde. Acts on both enantiomers. (R)-carnitine + H(+) + NADH + O2 = (3R)-3-hydroxy-4-oxobutanoate + H2O + NAD(+) + trimethylamine (R)-carnitine + H(+) + NADPH + O2 = (3R)-3-hydroxy-4-oxobutanoate + H2O + NADP(+) + trimethylamine Binds 1 [2Fe-2S] cluster per subunit. Binds 1 Fe cation per subunit. Inhibited by EDTA. Amine and polyamine metabolism; carnitine metabolism. Composed of an oxygenase subunit and a reductase subunit. Belongs to the bacterial ring-hydroxylating dioxygenase alpha subunit family. CntA subfamily.