An NAD‐linked lactate dehydrogenase (LDH) in a crude mitochondrial fraction obtained from Tetrahymena homogenates was previously reported by this laboratory. This fraction contains the NADH and succinate oxidase system as well as the mitochondrial cytochromes and carries out oxidative phosphorylation. The preparation catalyzes the oxidation of D‐ and L‐lactate linked only to certain analogs of NAD; it has not been possible to demonstrate NAD‐dependent D‐ or L‐lactate oxidation nor is there any evidence that either of these enzymes is a flavoprotein as indicated by their inability to reduce directly certain artificial electron acceptors. A lactate racemase is not present.

中文翻译：

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四膜虫的吡啶核苷酸连接的乳酸脱氢酶：线粒体中 D 和 L 酶的证据

该实验室先前报道了从四膜虫匀浆中获得的粗线粒体部分中的 NAD 连接的乳酸脱氢酶 (LDH) 。该部分包含 NADH 和琥珀酸氧化酶系统以及线粒体细胞色素并进行氧化磷酸化。该制剂催化仅与某些 NAD 类似物连接的 D-和 L-乳酸的氧化；不可能证明 NAD 依赖的 D-或 L-乳酸氧化，也没有任何证据表明这些酶中的任何一种是黄素蛋白，因为它们无法直接还原某些人工电子受体。不存在乳酸消旋酶。