<s>[INST] context: The isoenzyme of lactate dehydrogenase(LDH). active muscle tissue becomes anaerobic and produces pyruvate from glucose glycolysis, it needs LDH to regenerate NAD+ from NADH so that glycolysis can continue. the lactate produced is released into the blood. the musclesLDH isozyme(A4) works best in the NAD+ regenerating direction. hea tissue is aerobic and uses lactate as a fuel. conveing it into pyruvate too fule the citric acid cycle to obtain energy. the hea LDH isoenzyme(B$) is inhibited by excess pyruvate so that the fuel won&;t be wasted.Lactate dehydrogenase (LDH or LD) is an enzyme found in nearly all living cells (animals, plants, and prokaryotes). LDH catalyzes the conversion of lactate to pyruvic acid and back, as it conves NAD+ to NADH and back. A dehydrogenase is an enzyme that transfers a hydride from one molecule to another.LDH exists in four distinct enzyme classes. This aicle is specifically about the NAD(P)-dependent L-lactate dehydrogenase. Other LDHs act on D-lactate and/or are dependent on cytochrome c: D-lactate dehydrogenase (cytochrome)) and L-lactate (L-lactate dehydrogenase (cytochrome)).LDH is expressed extensively in body tissues, such as blood cells and hea muscle. Because it is released during tissue damage, it is a marker of common injuries and disease such as hea failure. [/INST] question: Which is predominant in normal healthy human? | options: A: LDH1 B: LDH2 C: LDH3 D: LDH4 | answer: B </s>