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Propionyl CoA carboxylase (PCC) is a mitochondrial, biotin-dependent enzyme involved in the catabolism of amino acids, odd-chain fatty acids, and other metabolites. PCC consists of two subunits, alpha and beta, encoded by the PCCA and PCCB genes, respectively. Inherited PCC deficiency due to mutations in either gene results in propionic acidemia (PA), an autosomal recessive disease. Surprisingly, PA is highly prevalent among Inuits in Greenland. We have analyzed reverse transcriptase-PCR products of the beta-subunit mRNA, to characterize the responsible mutation(s). A 3-bp insertion, 1540insCCC, was found in homozygous form in three patients and in compound heterozygous form in one patient. The resulting PCC has no measurable activity, and the mutant beta-subunit appears to be very unstable. To test the hypothesis that a common mutation is responsible for PA in the Greenlandic Inuit population, 310 anonymous DNA samples of Inuit origin were screened for 1540insCCC. We found a carrier frequency of 5%, which is very high compared with those of most other autosomal recessive diseases. Analysis of alleles of a very closely linked marker, D3S2453, revealed a high degree of linkage disequilibrium between one specific allele and 1540insCCC, suggesting that this mutation may be a founder mutation.

Glutaric acidemia type I (GAI) (McKusick 231670) is an autosomal recessive disease affecting the catabolism of the amino acids lysine, hydroxylysine and tryptophan, caused by a defect in the gene encoding glutaryl-coenzyme A dehydrogenase (GCDH) and associated with severe neurological symptoms. Several pathogenic mutations in GCDH have been reported to cause GAI. One mutation, R402W, is more common than the others, which seem to be private" mutations. Here we report the entire sequences of introns 1, 2, 3, 6, 7, 8 and 9, and part of those of introns 4, 5 and 10 as well as 21 different mutations in 20 patients with GAI, corresponding to 38 out of 40 alleles.

Five urine samples were collected in clinically quiet periods over a period of one year from a patient suffering from D-glyceric acidemia, and investigated for presence or absence of glycine-conjugates. The findings of isovalerylglycine, 2-methylbutyrylglycine, isobutyrylglycine, and tiglylglycine are interpreted as indications of intracelluar accumulations of isovaleryl-CoA, 2-methylbutyryl-CoA and isobutyryl-CoA. Similarly, the findings of elevated amounts of butyric acid and hexanoic acid together with butyrylglycine, hexanoylglycine, and suberic acid suggest intracellular accumulations of straight-chain acyl-CoA's. It is therefore suggested that this child has a common derangement in his acyl-CoA dehydrogenase (in addition to his primary defect). As possible secondary consequences of this, two points can be mentioned: firstly hyperglycinemia, from which the patient suffered, and secondly, diminished tendency to ketosis, a condition from which the child never suffered, not even in connection with severe intercurrent disease.

Citrullinaemia was presumed to be excluded in a fetus at risk by the direct assay of argininosuccinate synthetase in chorionic villi. The diagnosis was confirmed after amniocentesis by normal argininosuccinate synthetase activity in the cultured amniotic fluid cells and by a normal citrulline concentration in the amniotic fluid. The prediction of a normal fetus was confirmed at term by the birth of a non-citrullinaemic boy.

The autosomal recessive inherited disorder glutaryl-CoA dehydrogenase deficiency (glutaric aciduria) runs a progressive course with severe choreoathetosis and dystonia, eventually leading to total helplessness and early death. Theree patients were observed during therapeutic trials with a protein-low diet, riboflavin and GABA analogue. Diet and riboflavin had a slight-to-moderate effect on the clinical symptoms; the excretion of glutaric acid and 2-amino-adipic acid decreased considerably during treatment. Regression of neurologic symptoms was observed during treatment with GABA analogue. It is concluded that the patients should be treated as early as possible with protein-low diet, riboflavin, and GABA analogue.

In two siblings with dystonic cerebral palsy the urinary metabolic profiles of organic acids were dominated by glutaric acid, a metabolite not normally present in urine. The exretion of glutaric acid amounted to several grams per day. The urinary excretion of beta-OH-glutaric acid and glutaconic acid was also enhanced. Imparied metabolism of glutaryl-CoA by leukocytes indicates that the patients suffer from an inborn error of lysine, tryptophan, and hydroxylysine metabolism. A defective oxidation of glutaryl-CoA to crotonyl-CoA, probably due to a deficiency of glutaryl-CoA dehydrogenase, is consistent with these findings.

Succinylacetone was excreted in the urine from four patients, with hereditary tyrosinemia i.e., two patients with the severe infantile type with fatal outcome and two patients with less severe juvenile form. In the urine from two patients with neonatal transient tyrosinemia and from normal individuals succinylacetone was not detectable. The urinary excretion of delta-aminolevulinic acid was also increased in all patients with hereditary tyrosinemia compared to patients with neonatal transient tyrosinemia and to normal individuals. The results presented support the hypothesis of a deficiency of fumarylacetoacetase in hereditary tyrosinemia. Furthermore an analytical method for the quantitative determination of succinylacetone in urine using GC-MS is described.

Argininosuccinate synthetase activity in amniotic fluid cells from a fetus at risk for citrullinaemia was low compared to the activity in amniotic fluid cells from a normal fetus, but five times the activity in fibroblasts from a patient with citrullinaemia. These enzyme values indicated indicated a normal or heterozygous fetus. Chromosome analysis of the amniotic fluid cells from the fetus at risk, however, showed an unusual X/20 translocation. As we could not guarantee the delivery of a normal child, the parents chose to have a therapeutic abortion. Argininosuccinate synthetase activity in the liver and kidney of the aborted fetus was in the normal and heterozygous range respectively, confirming the prenatal diagnosis. The activity in the father's fibroblasts was low, less than 10% of normal. The difficulty of interpreting the results of prenatal diagnosis in such a family and the importance of studying parental cells are discussed.

Studies of a mentally retarded boy, clinically suffering from nonketotic hyperglycinemia, are reported. Using combined gas chromatography-mass spectrometry, enzyme specificity studies, and spectropolariometry D-glyceric acid in extremely elevated concentrations was demonstrated in both serum and urine (serum: 1.0-1.3 mmol/liter, urine: 33-187 mmol/liter). Hydroxypyruvic acid was not detectable in urine from this boy using a gas chromatographic method with a limit of detection of 0.3 mmol/liter. Enzyme assays of D-glyceric dehydrogenase on blood leukocytes demonstrated significantly lower activity in the patient compared with five normal children.

The glycine uptake in cultured fibroblasts was studied in three children with non-ketotic hyperglycinaemia, one child with D-glyceric acidaemia and hyperglycinaemia and in six normal children, using an improved assay system giving individual protein correction. It was shown that all hyperglycinaemic children had normal uptake rates and kinetic characteristics similar to the controls.

A mentally retarded boy exhibiting both hyper-D-glyceric acidemia and hyperglycinemia and in whom a deficiency of D-glycerate dehydrogenase had previously been demonstrated was investigated to elucidate the ethiology of the glycine accumulation and its relationship to the D-glyceric acid accumulation. It was found that a positive correlation existed between excretion of D-glyceric acid and glycine (coefficient of correlation: r = 0.62, P < 0.001), that part of the IV injected [14C]glycine was metabolized to D-glyceric acid whereas no [14C]glyceric acid was metabolized to glycine, and that the in vivo degradation of IV injected [14C]glycine to 14CO2 was diminished. Measurement of glycine cleavage activity in autoptic liver tissue from the patient showed only 10% of normal activity. It is argued that this diminished activity could be caused by an endogenous inhibitor. D-glyceric acid is demonstrated not to possess such an inhibitory effect. Based on the finding of increased urinary excretion of both free and conjugated isobutyric acid, 2-methylbutyric acid, and isovaleric acid, it is hypothesized that the diminished glycine cleavage activity might be due, at least partially, to inhibition by 2-methylbutyryl-CoA and isobutyryl-CoA, two compounds that are known to inhibit the glycine cleavage system.

The clinical and laboratory findings in a 2 1/2-year-old boy with non-ketotic hyperglycinaemia are reported. Except for a somewhat impaired liver function there was a picture similar to the cases previously reported in the literature. The patient deviated from the classical description, however, in the excretion of large amounts of D-glyceric acid in the urine. The same compound was also repeatedly found in the serum. It is suggested that the large amounts of glycine found in various body fluids are secondary to a hitherto undescribed enzymatic defect in the degradation of D-glyceric acid.

A patient exhibiting progressive cerebral depression from the first days of life is described. The diagnosis of nonketotic hyperglycinemia was established on the typical clinical presentation, elevated glycine concentrations in body fluids and diminished glycine cleavage activity in liver tissue. A series of therapeutic trials, including strychnine treatment, was tried on this patient without apparent effect on the clinical course.