Enzymological aspects of disorders in purine metabolism

Congenital enzyme defects of purine synthesis de novo and the salvage pathway are responsible for excessive uric acid production and are often associated with hyperuricemia and gout. On the other hand, defects of enzymes essential for the purine nucleotide cycles are the biochemical basis of dysfunction of the immune system. The influence of several congenital enzyme deficiencies on the regulation of biosynthesis de novo, on the regulation of purine nucleotide concentrations, and on adenosine concentration, as well as the effect on purine transport through cell membranes are discussed. The determination of enzymes involved in purine metabolism in noncongenital diseases seems to be of diagnostic importance. As examples, enzyme activities in lymphocytes of leukemic patients, and the determination of serum guanase activity in patients with liver dysfunction are described.