好酸性細菌 Acidiphilium organovorum 由来のアラニンセマーゼ

Alanine racemase(EC 5.1.1.1)was screened from several acidophilic bacteria.Acidiphilium organovorum 13H showed the highest activity and was chosen as the representative source to study alaine racemase from acidphlic bacteria.The enzyme was found to be localised in the cytoplasm of the bacteria.Relative molecular mass syudies indicated that it had a dimeric native structure with identical subunits of about 34 kDa each.Maximum activity was observed between 50 and 60℃and at pH9.There was no loss of enzyme activity even after incubation at 65℃.The loss of activity upon dialysis against pyridoxal 5'-phosphate-free buffer containing hydroxylamine,and its partial recovery upon subsequent dialysis against buffer containing phyridoxal 5'-phosphate suggested that the enzyme required piridoxal 5'-phosphate as a co-factor for its catalytic activity.