Soemphol Wichai, Adachi Osao, Matsushita Kazunobu, Toyama Hirohide
Department of Biological Chemistry, Faculty of Agriculture, Yamaguchi University, Yamaguchi 753-8515, Japan.
Biosci Biotechnol Biochem. 2008 Mar;72(3):842-50. doi: 10.1271/bbb.70720. Epub 2008 Mar 7.
Two different membrane-bound enzymes oxidizing D-sorbitol are found in Gluconobacter frateurii THD32: pyroloquinoline quinone-dependent glycerol dehydrogenase (PQQ-GLDH) and FAD-dependent D-sorbitol dehydrogenase (FAD-SLDH). In this study, FAD-SLDH appeared to be induced by L-sorbose. A mutant defective in both enzymes grew as well as the wild-type strain did, indicating that both enzymes are dispensable for growth on D-sorbitol. The strain defective in PQQ-GLDH exhibited delayed L-sorbose production, and lower accumulation of it, corresponding to decreased oxidase activity for D-sorbitol in spite of high D-sorbitol dehydrogenase activity, was observed. In the mutant strain defective in PQQ-GLDH, oxidase activity with D-sorbitol was much more resistant to cyanide, and the H(+)/O ratio was lower than in either the wild-type strain or the mutant strain defective in FAD-SLDH. These results suggest that PQQ-GLDH connects efficiently to cytochrome bo(3) terminal oxidase and that it plays a major role in L-sorbose production. On the other hand, FAD-SLDH linked preferably to the cyanide-insensitive terminal oxidase, CIO.
在弗氏葡萄糖杆菌THD32中发现了两种氧化D-山梨醇的不同膜结合酶：吡咯喹啉醌依赖性甘油脱氢酶（PQQ-GLDH）和黄素腺嘌呤二核苷酸依赖性D-山梨醇脱氢酶（FAD-SLDH）。在本研究中，FAD-SLDH似乎是由L-山梨糖诱导产生的。两种酶均有缺陷的突变体与野生型菌株生长情况相同，这表明这两种酶对于在D-山梨醇上生长并非必需。PQQ-GLDH有缺陷的菌株L-山梨糖产量延迟，且积累量较低，尽管D-山梨醇脱氢酶活性较高，但观察到其D-山梨醇氧化酶活性降低。在PQQ-GLDH有缺陷的突变菌株中，D-山梨醇的氧化酶活性对氰化物的抗性更强，且H(+)/O比值低于野生型菌株或FAD-SLDH有缺陷的突变菌株。这些结果表明，PQQ-GLDH能有效地与细胞色素bo(3)末端氧化酶相连，且在L-山梨糖的产生中起主要作用。另一方面，FAD-SLDH则优先与对氰化物不敏感的末端氧化酶CIO相连。
