The excretion of the aminoketones, aminoacetone (AA) and 5-aminolevulinic acid (ALA) has been studied in 7 children. One of the children had ketotic hyperglycinemia and one had nonketotic hyperglycinemia. The formation of these aminoketones has been studied in vivo using 14C-labeled glycine and threonine. The amounts of AA in the urine were slightly smaller than those of ALA in the subjects studied. Neither was increased by the infusion of large amounts of glycine. The amounts of aminoketone were independent of the concentrations of glycine in the plasma and did not differ from control in patients with disordered glycine metabolism. The amounts of aminoketone excreted varied directly with the weight of the child. The injection of labeled glycine did not yield labeled urinary AA but small amounts of labeled ALA were found. Significant labeling of urinary AA was found after the administration of labeled threonine. It is concluded that the metabolic precursor of urinary AA is threonine. Conversion to aminoketones, either AA or ALA, is not a major catabolic pathway for glycine in man. These pathways are not involved in either the etiology or the adaptation to hyperglycinemia. © 1969, Tohoku University Medical Press. All rights reserved.
