Biological Function
In general, SDH levels decrease with increasing mammalian size. In fact, mammals catabolize serine into pyruvate with the enzymes serine hydroxymethyltransferase and glycine cleavage enzymes rather than SDH.
Studies show that the SDH enzyme from rat hepatocytes plays an important role in gluconeogenesis; its activity is augmented by high-protein diets and starvation. During periods of low carbohydrates, serine is converted into pyruvate via SDH. This pyruvate enters the mitochondria where it can be converted into oxaloacetate, and, thus, glucose.
Figure 7 shows the possible routes of L-Serine conversion into glucose during gluconeogenesis.
However, interestingly, little is known about the properties and the function of human SDH because human liver has low SDH activity. In a study done by Yoshida and Kikuchi, routes of glycine breakdown were measured. Glycine can be converted into serine and either become pyruvate via serine dehydratase or undergo oxidative cleavage into methylene-THF, ammonia, and carbon dioxide. Results showed the secondary importance of the SDH pathway.
Read more about this topic: Serine Dehydratase
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