Serum carnosinase deficiency concomitant with mental retardation.

Extract: A family was studied in which two boys with progressive neurologic disease exhibited carnosinemia (20–30 μUmol/ml serum), carnosinuria (60–200 μUmol/24 hr), and a deficiency in serum carnosinase activity (<0.03 μUmol/hr/ml). Their sister, who is apparently both physically and mentally normal, also exhibits carnosinuria and is deficient in serum carnosinase activity. Tissue extracts of liver, kidney, and spleen obtained at autopsy of one of the male patients were assayed for carnosinase and other enzyme activities and were subjected to starch block electrophoresis at pH 7.0 for 4 hr at 4°. The starch block electrophoreses, under conditions which readily demonstrate two electrophoretic forms of the enzyme in normal tissue extracts, revealed that only one of the two forms was present. This activity corresponded to the slower form in normal tissues and appeared to be present in normal concentrations. Speculation: The excretion of abnormal quantities of carnosine and/or anserine in the urine appears to be related to inherited serum carnosinase deficiency, but further studies are required to determine the association of the deficiency of the enzyme with progressive neurologic disease as well as the nature and role of the two electrophoretic forms of tissue carnosinase activity.