Sakuno Emi, Kameyama Mayumi, Nakajima Hiromitsu, Yabe Kimiko
Department of Agricultural Chemistry, Faculty of Agriculture, Tottori University, Tottori 680-8553, Japan.
Biosci Biotechnol Biochem. 2008 Mar;72(3):724-34. doi: 10.1271/bbb.70597. Epub 2008 Mar 7.
When 10 strains of lactic acid bacteria were incubated with 5'-hydroxyaverantin (HAVN), a precursor of aflatoxins, seven of them converted HAVN to averufin; the same reaction is found in aflatoxin biosynthesis of aflatoxigenic fungi. These bacteria had a dehydrogenase that catalyzed the reaction from HAVN to 5'-oxoaverantin (OAVN), which was so unstable that it was easily converted to averufin. The enzyme was purified from Lactobacillus brevis IFO 12005. The molecular mass of the enzyme was 100 kDa on gel filtration chromatography and 33 kDa on SDS polyacrylamide gel electrophoresis (SDS-PAGE). The gene encoding the enzyme was cloned and sequenced. The deduced protein consisted of 249 amino acids, and its estimated molecular mass was 25,873, in agreement with that by time of flight mass spectrometry (TOF MS) analysis. Although the deduced amino acid sequence showed about 50% identity to those reported for alcohol dehydrogenases from L. brevis or L. kefir, the commercially available alcohol dehydrogenase from L. kefir did not convert HAVN to OAVN. Aspergillus parasiticus HAVN dehydrogenase showed about 25% identity in amino acid sequence with the dehydrogenase and also with these two alcohol dehydrogenases.
当10株乳酸菌与黄曲霉毒素的前体5'-羟基奥佛菌素（HAVN）一起培养时，其中7株将HAVN转化为奥佛精；在产黄曲霉毒素真菌的黄曲霉毒素生物合成中也发现了相同的反应。这些细菌有一种脱氢酶，可催化从HAVN到5'-氧代奥佛菌素（OAVN）的反应，而OAVN非常不稳定，很容易转化为奥佛精。该酶从短乳杆菌IFO 12005中纯化得到。在凝胶过滤色谱上该酶的分子量为100 kDa，在SDS聚丙烯酰胺凝胶电泳（SDS-PAGE）上为33 kDa。编码该酶的基因被克隆并测序。推导的蛋白质由249个氨基酸组成，其估计分子量为25,873，与飞行时间质谱（TOF MS）分析结果一致。尽管推导的氨基酸序列与报道的来自短乳杆菌或开菲尔乳杆菌的乙醇脱氢酶的氨基酸序列显示出约50%的同一性，但市售的来自开菲尔乳杆菌的乙醇脱氢酶不能将HAVN转化为OAVN。寄生曲霉HAVN脱氢酶在氨基酸序列上与该脱氢酶以及这两种乙醇脱氢酶显示出约25%的同一性。
