Oren A, Gurevich P
Division of Microbial and Molecular Ecology, Alexander Silverman Institute of Life Sciences, Jerusalem, Israel.
Can J Microbiol. 1995 Mar;41(3):302-7. doi: 10.1139/m95-042.
D-Lactate is readily used as a substrate for the growth of species of halophilic archaea belonging to the genera Haloferax and Haloarcula. L-Lactate was used by Haloferax species (Haloferax volcanii, Haloferax mediterranei) only when a substantial concentration of the D-isomer was also present in the medium. On the enzymatic level, considerable diversity was found in the lactate metabolism of the different representatives of the Halobacteriaceae. At least three types of lactate dehydrogenases were detected in halophilic archaea. A high level of activity of an NAD-linked enzyme was present constitutively in Haloarcula species, and a low level of activity was also detected in Haloferax mediterranei. NAD-independent lactate dehydrogenases, oxidizing L-lactate and D-lactate with 2,6-dichlorophenol-indophenol as electron acceptor, were detected in all nine species tested, but L-lactate dehydrogenase activity in Halobacterium species was very low, and Haloarcula species, which possess a high level of activity of NAD-linked lactate dehydrogenase, showed very low activities of both NAD-independent D- and L-lactate dehydrogenase. An inducible lactate racemase, displaying an unusually high pH optimum, was found in Haloferax volcanii. Lactate racemase activity was found constitutively in Haloarcula species, but no activity was detected in Halobacterium species and in Haloferax mediterranei.
D-乳酸很容易被用作嗜盐古菌属（如嗜盐栖热菌属和嗜盐碱杆菌属）物种生长的底物。只有当培养基中也存在大量浓度的D-异构体时，嗜盐栖热菌属物种（沃氏嗜盐栖热菌、地中海嗜盐栖热菌）才会利用L-乳酸。在酶水平上，发现盐杆菌科不同代表菌的乳酸代谢存在相当大的差异。在嗜盐古菌中至少检测到三种类型的乳酸脱氢酶。嗜盐碱杆菌属物种中组成型存在高水平的NAD连接酶活性，在地中海嗜盐栖热菌中也检测到低水平的活性。在所有测试的九个物种中都检测到了不依赖NAD的乳酸脱氢酶，它们以2,6-二氯酚靛酚作为电子受体氧化L-乳酸和D-乳酸，但盐杆菌属物种中的L-乳酸脱氢酶活性非常低，而具有高水平NAD连接乳酸脱氢酶活性的嗜盐碱杆菌属物种，其不依赖NAD的D-和L-乳酸脱氢酶活性都非常低。在沃氏嗜盐栖热菌中发现了一种诱导型乳酸消旋酶，其最适pH异常高。在嗜盐碱杆菌属物种中组成型存在乳酸消旋酶活性，但在盐杆菌属物种和地中海嗜盐栖热菌中未检测到活性。
