에탄올 대사 과정에서 생성된 acetaldehyde를 산화하는 aldehyde dehydrogenase(ALDH)의 간세포 소기관 내의 분포를 조사하고 세 가지의 미크로좀 aldehyde dehydrogenase를 분리, 정제하여 그들의 특성을 조사하였다. Aldehyde dehydrogenase의 세포 내 활성 분포는 미토콘드리아, 시토졸, 미크로좀에 각각 51, 17, 32%로서 절반은 미토콘드리아에 편중되어 있었으나 미크로좀에도 상당량이 존재함을 확인하였다. Ammonium sulfate 침전, gel filtration, DEAE cellulose, CM-cellulose, blue sepharose affinity chromatography법 등을 이용하여 세 가지 미크로좀 aldehyde dehydrogenase, 즉 ALDH-I, ALDA-II, ALDH-III가 분리되었고 acetaldehyde에 대한 Km은 각각 2.77, 3.5, 1.56mM이었으며 다른 aldehyde, 즉 propionaldehyde, glutaraldehyde에 대해서도 활성을 나타내었다. Sephacryl S-300 gel filtration 법으로 분자량을 측정한 결과 미크로좀 aldehyde dehydrogenase isozyme I, II, III의 분자량은 각각 220,000 dalton, 170,000 dalton, 200,000 dalton이고 SDS polyacrylamide gel 전기이동법으로 모두 4개의 subunit로 구성된 tetramer임이 밝혀지고 최적 활성온도는 $40^{circ}C$, 최적 활성 pH는 8.0이었다. 미크로좀의 에탄올 산화계 (MEOS)에 의해 생성된 acetaldehyde는 Km이 높은 microsomal ALDH에 의해 직접 대사되는 것으로 추측된다.
Rat liver microsomal aldehyde dehydrogenase (ALDH) isozymes were purified and their properties were investigated. A significant fraction (32%) of the total ALDH activity was found in microsomal fraction but a small activity was also in cytosol fraction (17%). 51% of the total ALDH activity was found in mitochondria. Three ALDH isozymes were purified from the rat liver microsomal fraction using ammonium sulfate precipitation, gel filtration, DEAE cellulose chromatography, CM-cellulose chromatography, blue sepharose affinity chromatography techniques. The $K_m$ (for acetaldehyde) of microsomal ALDH-I, ALDH-II, ALDH-III were 2.77 mM, 3.5 mM, 1.56 mM respectively. Purified ALDH-I, -II and -III were estimated to have molecular weight of 220,000, 170,000 and 20,000 dalton respectively by sephacryl S-300 gel filtration and all of them were found to be composed of four subunits by SDS polyacrylamide gel electrophoresis. The optimum pH for these enzymes was 8.0 and optimum temperature was $40^{circ}C$. It was realized that the acetaldehyde formed by microsomal ethanol oxidizing system (MEOS) might be metabolized directly by the action of microsomal aldehyde dehydrogenases.
