Lactate dehydrogenase deficiency

**Definition:** This refers to a deficiency in the enzyme present in a wide variety of organisms, including plants and animals. This exists in four distinct enzyme classes. Two of them are cytochrome c-dependent enzymes, each acting on either D-lactate (EC 1.1.2.4) or L-lactate (EC 1.1.2.3). The other two are NAD(P)-dependent enzymes, each acting on either D-lactate (EC 1.1.1.28) or L-lactate (EC 1.1.1.27). This article is about the NAD(P)-dependent L-lactate dehydrogenase.