A cobalamin metabolic defect with homocystinuria, methylmalonic aciduria and macrocytic anemia.

We have identified a patient with methylmalonic aciduria and homocystinuria due to a defect in cobalamin metabolism of the cb1C type mutant. At the time of admission at eight months of age the patient was malnourished, hypotonic and had macrocytic anemia. Neonatal screening for hypermethioninemia associated with homocystinuria had been normal.

Taurine uptake by cultured human lymphoblastoid cells.

Cultured human lymphoblastoid cells take up taurine from the medium by two processes: 1) a temperature-dependent, Na+-dependent, saturable "active"-transport system and 2) diffusion. The active transport has properties similar to those reported for taurine transport by other tissues. Apparent Km is about 25 microM and Vmax about 7.

Ornithine carbamoyltransferase deficiency in an adult male patient: significance of hepatic ultrastructure in clinical diagnosis.

Ornithine carbamoyltransferase (OCT) activity was deficient (8% of control) in the liver of a 21-year-old man who died after suddenly becoming comatose. Activities of other enzymes of the urea cycle in the liver were normal. There was no known prior illness or injury; the patient, however, had been taking liquid protein supplements to his diet.

Intermittent hypermethioninaemia associated with normal hepatic methionine adenosyltransferase activity: report of a case.

A 5-month-old infant was found to have hypermethioninaemia (0.8 mumol/ml) that has persisted intermittently (0.02-1.

Methioninemia and myopathy: a new disorder.

A 7 1/2-year-old girl with hypermethioninemia, myopathy, and mental deficiency (IQ = 65) is described. The increased methionine was not associated with deficiency of methionine adenosyltransferase, which was normal or increased in liver, muscle, erythrocytes, and cultured fibroblasts. Methionyl-tRNA synthetase in fibroblasts was normal.

Hypermethioninemia associated with methionine adenosyltransferase deficiency: clinical, morphologic, and biochemical observations on four patients.

Four patients with hypermethioninemia were ascertained in neonatal mass metabolic screening programs. Hypermethioninemia has persisted in all cases. There were no other abnormalities in sulfur-amino acid concentrations, and routine serum chemical determinations, including the results of "liver function" tests, were normal.

Mitochondrial abnormalities of liver in primary ornithine transcarbamylase deficiency.

Deficiency of hepatic ornithine transcarbamylase (EC 2.1.3.

Cystathionase deficiency: the effect of cofactor on the stability of normal and abnormal enzyme from lymphoid cell lines.

Heating at 70 degrees C with and without added pyridoxal phosphate (PLP) had strikingly different effects on cystathionase protein from normal long-term lymphoid cell lines and on the enzymes from cells derived from patients with vitamin-B6-responsive cystathioninuria. PLP added to extracts of normal cells afforded complete protection against heat inactivation, whereas inactivation of the cystathionase protein in extracts obtained from two cystathioninuric lines was greater in the presence of PLP than in its absence.

Cystathionine beta-synthase deficiency: a qualitative abnormality of the deficient enzyme modified by vitamin B6 therapy.

The thermostability of cystathionine synthase and the effect of pyridoxal phosphate (PLP) on this thermostability were investigated in extracts of normal human liver and in extracts of liver, both before and during pyridoxine (vitamin B6) therapy, from members of a family with three clinically and biochemically typical, B6-responsive, synthase-deficient sibs. Incubation of crude extracts of normal liver at 55 degrees (preincubation) for 3-4 min before assay consistently resulted in a more than 2-fold increase in specific activity (activation) of cystathionine synthase (Fig. 1).

Vitamin B6-responsive and -unresponsive cystathioninuria: two variant molecular forms.

Cystathionase activity in a lymphoid cell line extracts from a vitamin B6-responsive patient with cystathioninuria was increased strikingly by pyridoxal phosphate. Immunodiffusion with antiserum to human hepatic cystathionase showed identity between this cystathionase protein and cystathionase from an extract of normal lymphoid cells. Neither an increase in cystathionase activity nor immunochemical identity was found using extract of cells from a B6-unresponsive patient.

Methionine adenosyltransferase deficiency: new enzymatic defect associated with hypermethioninemia.

A specific deficiency of methionine adenosyltransferase has been demonstrated in the liver of an infant with hypermethioninemia. Since the enzymatic activity was below that in fetal liver and the metabolic abnormality has persisted (the infant now being 1 year of age), there is probably a genetic mutation. Mass screening for hypermethioninemia may uncover more such cases.