Wistar계 흰 쥐의 뇌 시토졸의 aldehyde reductase(ALR)들을 황산 암모늄 분별 침전, DEAE-Sepharose CL-6B ion exchange chromatography, Blue-Sepharose CL-6B affinity chromatography, hydroxylapatite chromatography를 이용하여 분리 정제하였다. 그 중 p-nitrobenzaldehyde에 대한 $K_m$값이 낮은 것($45;{mu}M$)을 low $K_m$ ALR, 큰 것($160;{mu}M$)을 high $K_m$ ALR이라고 하였다. 이 두 isozyme은 모두 SDS-PAGE 상에서 단일 띠로 나타났으며 Sephacryl S-200 gel filtration을 수행한 결과 분자량이 각각 72,000dalton과 42,000dalton이었다. 이 효소들의 최적 촉매 pH는 high $K_m$ ALR이 6.5, low $K_m$ ALR이 6.0이었고 두 isozyme은 $37^{circ}C$ 에서는 상당히 안정하며 $50^{circ}C$, $70^{circ}C$로 온도가 높아질수록 짧은 시간 내에 활성이 급격히 상실되었으나 low $K_m$ ALR은 high $K_m$ ALR에 비해 좀 더 안정하였다. 몇 가지 기질에 대한 low $K_m$ ALR과 high $K_m$ ALR의 $K_m$값을 조사한 결과 대부분의 aldehyde에 대해 low $K_m$ ALR이 high $K_m$ ALR 보다 낮은 $K_m$값을 가지는 것으로 나타났으나, succinic semialdehyde에 대하여는 유달리 high $K_m$ ALR의 $K_m$값이 낮았다. $V_{max}/K_m$을 친화력의 척도로 사용하였을 때 두 ALR isozyme이 모두 aliphatic aldehyde 보다는 aromatic aldehyde에 대한 결합력이 컸다. High $K_m$ ALR은 succinic semialdehyde에 대한 결합력이 크고 $K_m$값이 낮아서 $gamma$-hydroxybutyrate 대사와 밀접한 관련이 있으며, low $K_m$ ALR은 biogenic aldehyde의 대사에서 중요한 역할을 하는 것으로 생각된다.
Cytosolic aldehyde reductase (ALR) isozymes of Wister rat brain were purified by ammonium sulfate precipitation, DEAF-Sepharose CL-6B ion exchange chromatography, Blue-Sepharose CL-6B affinity chromatography, and hydroxylapatite chromatography. ALR having low $K_m$ ($45;{mu}M$) for p-nitrobenzaldehyde was named low $K_m$ ALR, and ALR with high $K_m$ ($160;{mu}M$) for p-nitrobenzaldehyde was named high $K_m$ ALR. These two isozymes showed a single band on SDS-polyacrylamide gel electrophoresis. The molecular weights were deter-mined according to Sephacryl S-200 gel filtration and found to be 72,000 dalton and 42,000 dalton, respectively. The optimal pH of high $K_m$ ALR was 6.5 and that of low $K_m$ ALR was 6.0 Two isozymes were very stable at $37^{circ}C$ but the activity rapidly decreased as the tempera-ture increased to $50^{circ}C$ and/or $70^{circ}C$. However low $K_m$ ALR seemed to be more stable to temperature than high $K_m$ ALR. $K_m$ values of low $K_m$ ALR and high $K_m$ ALR for several substrates were determined. Low $K_m$ ALR showed lower $K_m$ values than those of high $K_m$ ALR for most aldehydes, but $K_m$ value of high $K_m$ ALR for succinic semialdehyde was particularly low. When $V_{max}/K_m$ ratio was considered, both isozymes have stronger affinity for aroma-tic aldehydes than aliphatic aldehydes. High $K_m$ ALR seems to have close relationship to $gamma$-hydroxybutyrate metabolism since it has strong affinity for succinic semialdehyde, and low $K_m$ ALR seems to play an important role in the metabolism of biogenic aldehyde.
