Aldehyde dehydrogenase 1B1 (ALDH1B1): Molecular cloning and characterization of a novel mitochondrial acetaldehyde metabolizing enzyme

Ethanol-induced damage is largely attributed to its toxic metabolite, acetaldehyde. Clearance of acetaldehyde is achieved by its oxidation, primarily catalyzed by the mitochondrial class II aldehyde dehydrogenase (ALDH2). ALDH1B1 is another mitochondrial A LDH t hat s hares 75% peptide sequence h omology w ith A LDH2. R ecent p opulation studies in C aucasians suggest a r ole f or ALDH1B1 in e thanol m etabolism. Ho wever, to da te, no f ormal documentation of t he biochemical pr operties of A LDH1B1 ha s been f orthcoming. I n th is current study, we c loned a nd expressed human r ecombinant ALDH1B1 in S f9 insect cells. The resultant enzyme was purified by affinity c hromatography to homogeneity. The kine tic properties o f pur ified h uman A LDH1B1 w ere a ssessed using a w ide range o f a ldehyde substrates. Human ALDH1B1 had an exclusive preference for NAD + as the cofactor and was catalytically active towards short-and medium-chain aliphatic aldehydes, aromatic aldehydes and the products of li pid pe roxidation, 4-hydroxy-nonenal (4-HNE) a nd malondialdehyde (MDA). M ost im portantly, hum an ALDH1B1 e xhibited an a pparent K m o f 55 μM f or acetaldehyde, making i t t he second low K m A LDH for m etabolism of t his su bstrate. The dehydrogenase activity of AL DH1B1 wa s s ensitive to d isulfiram in hibition, a feature a lso shared with ALDH2. The tissue distribution of ALDH1B1 in C57BL/6J mice and human was examined by Q-PCR, Western bl otting a nd im munohistochemical a nalysis. H ighest expression oc curred in th e li ver, f ollowed b y t he intestinal t ract, i mplicating a p otential physiological role of ALDH1B1 in these tissues. The current study is the first report on the expression, purification and biochemical characterization of human ALDH1B1 protein.