Chan Wing-Man, Tang Wai-Kwan, Cheng Christopher H K, Fong Wing-Ping
Department of Biochemistry, The Chinese University of Hong Kong, Shatin, NT, Hong Kong, PR China.
Comp Biochem Physiol B Biochem Mol Biol. 2003 Nov;136(3):443-50. doi: 10.1016/s1096-4959(03)00248-3.
Aldehyde dehydrogenase (ALDH) is a superfamily of enzymes catalyzing the conversion of various aldehydes to the corresponding acids using the coenzymes NAD+ or NADP+. While mammalian ALDHs have been studied extensively, the non-mammalian ALDHs, notably those of teleostean origin, remain relatively unexplored. In our previous study on grass carp (Ctenopharyngodon idellus) liver ALDH, a significant amount of the ALDH activity did not adsorb on the alpha-cyanocinnamate Sepharose column which binds ALDH2. The objective of the present study was to purify the ALDH which accounts for this unadsorbed activity. Further chromatography on Affi-gel Blue agarose, followed by size exclusion on Superdex 200 successfully isolated this aldehyde-oxidizing activity. The protein was a homo-tetramer with a subunit molecular mass of 58 kDa. N-terminal sequencing of the first 21 amino acid residues, followed by blastp analysis on the NCBI database revealed the protein as antiquitin. The optimal pH for the oxidation of acetaldehyde was 9.5. At this pH, the Vmax and the Km values for acetaldehyde were 1.95 U/mg and 2.00 mM, respectively.
醛脱氢酶（ALDH）是一类酶的超家族，利用辅酶NAD⁺或NADP⁺催化各种醛转化为相应的酸。虽然哺乳动物的ALDH已得到广泛研究，但非哺乳动物的ALDH，尤其是硬骨鱼类来源的ALDH，仍相对未被探索。在我们之前对草鱼（Ctenopharyngodon idellus）肝脏ALDH的研究中，大量的ALDH活性未吸附在结合ALDH2的α-氰基肉桂酸琼脂糖柱上。本研究的目的是纯化导致这种未吸附活性的ALDH。通过在Affi-gel Blue琼脂糖上进一步色谱分离，随后在Superdex 200上进行尺寸排阻，成功分离出了这种醛氧化活性。该蛋白质是一种同四聚体，亚基分子量为58 kDa。对前21个氨基酸残基进行N端测序，随后在NCBI数据库上进行blastp分析，结果显示该蛋白质为抗泛素蛋白。乙醛氧化的最适pH为9.5。在此pH下，乙醛的Vmax和Km值分别为1.95 U/mg和2.00 mM。
