 Although there is much controversy over the role of SDH in human hepatocytes, studies have shown that nonketotic hyperglycemia is due to the deficiency of threonine dehydratase, a close corollary to serine dehydratase.Serine dehydratase has also been found to be absent in human colon carcinoma and rat sarcoma.The observed enzyme imbalance in these tumors shows that an increased capacity for the synthesis of serine is coupled to its utilization for nucleotide biosynthesis as a part of the biochemical commitment to cellular replication in cancer cells.