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Summary Another example of a transport defect involving both renal tubular and intestinal epithelium is provided by the report of a patient with familial iminoaciduria who had impaired absorption of proline from the bowel and increased urinary clearances of iminoacids and glycine.

A patient with abnormalities of skeleton, eyes, ears and cardiovascular system, associated with iminodipeptiduria and bound hydroxyprolinuria, is described. Analysis of dermal collagen indicated decreased intermolecular cross linking, and electron microscopy of vascular collagen in the spleen disclosed abnormalities similar to those observed in lathyritic animals. These findings suggest that the clinical picture in this patient may represent a condition in man analogous to lathyrism in animals.

Studies are reported on a patient with free hydroxylysinemia and hydroxylysinuria. The results indicate the metabolism of appreciable quantities of free hydroxylysine in normal children, and are compatible with a defect in this catabolic pathway in the patient. Although the precise location of the metabolic block is not proved, it is suggested to lie at the level of hydroxy- l -lysine kinase.

Electron transfer flavoprotein (ETF) is a heterodimer that contains a single equivalent of FAD and accepts electrons from nine flavoprotein dehydrogenases in the mitochondrial matrix. Human ETF was expressed in Escherichia coli using the expression vector previously employed to express Paracoccus denitrificans ETF (Bedzyk, L. A., Escudero, K. W., Gill, R. E., Griffin, K. J., and Frerman, F. E. (1993) J. Biol. Chem. 268, 20211-20217). cDNAs encoding the beta and alpha subunits of the human protein were inserted into the vector, mimicking the arrangement of the P. denitrificans genes in which coding sequences are joined by overlapping termination and initiation codons. A human ETF containing 30% P. denitrificans sequence at the amino terminus of the beta subunit was also expressed and purified. This chimeric ETF has 64% sequence identity with the human sequence in the substituted region. Kinetic constants of medium chain and short chain acyl-CoA dehydrogenases for the chimeric ETFs were slightly changed from those of human ETF; but, there are marked differences in the kinetic constants of sarcosine dehydrogenase and electron transfer flavoprotein-ubiquinone oxidoreductase with the two ETFs. Absorption spectra of the three redox states of human, chimeric, and P. denitrificans ETF flavins are identical. However, the flavin circular dichroism spectra of the three ETFs are characteristic for each species. The spectrum of the chimeric ETF has both human and P. denitrificans ETF features. The amplitude of the 436 nm band is identical to that of the of the human ETF flavin, but the amplitude of the 375 nm band is identical to that of the P. denitrificans ETF flavin. Thus, flavin in the chimeric ETF appears to be exposed to dipoles in the protein framework provided by human and bacterial sequences. These spectral data indicate that the flavin is located in the vicinity of the amino-terminal region of the beta subunit. The kinetic data suggest that the amino-terminal region of the beta subunit comprises part of the docking site for some primary dehydrogenases and electron transfer flavoprotein-ubiquinone oxidoreductase.

We have used radio-high pressure liquid chromatography to study the acyl-CoA ester intermediates and the acylcarnitines formed during mitochondrial fatty acid oxidation. During oxidation of [U-14C]hexadecanoate by normal human fibroblast mitochondria, only the saturated acyl-CoA and acylcarnitine esters can be detected, supporting the concept that the acyl-CoA dehydrogenase step is rate-limiting in mitochondrial beta-oxidation. Incubations of fibroblast mitochondria from patients with defects of beta-oxidation show an entirely different profile of intermediates. Mitochondria from patients with defects in electron transfer flavoprotein and electron transfer flavoprotein:ubiquinone oxido-reductase are associated with slow flux through beta-oxidation and accumulation of long chain acyl-CoA and acylcarnitine esters. Increased amounts of saturated medium chain acyl-CoA and acylcarnitine esters are detected in the incubations of mitochondria with medium chain acyl-CoA dehydrogenase deficiency, whereas long chain 3-hydroxyacyl-CoA dehydrogenase deficiency is associated with accumulation of long chain 3-hydroxyacyl- and 2-enoyl-CoA and carnitine esters. These studies show that the control strength at the site of the defective enzyme has increased. Radio-high pressure liquid chromatography analysis of intermediates of mitochondrial fatty acid oxidation is an important new technique to study the control, organization and defects of the enzymes of beta-oxidation.

Galactosaemia due to galactose-1-phosphate uridyltransferase deficiency (McKusick 23040) is associated, in the untreated patient, with gastrointestinal symptoms, hepatomegaly, hepatic dysfunction, cataracts, septicaemia and, eventually, mental retardation. Neonates with classical galactosaemia may also present with increased intracranial pressure, which is reported to resolve on a galactose-free diet (Huttenlocher et al., 1970; Belman et al., 1986). We describe a newborn with galactosaemia who died at 19 days of age with cerebral oedema unresponsive to medical management

An infant with severe, transient hypermethioninemia is reported. Although probably very rare, it should be noted that elevation of serum methionine may not necessarily reflect the presence of homocystinuria, hereditary tyrosinemia, or severe liver disease.

GA2 may be due to inherited deficiency of electron transfer flavoprotein (ETF) or ETF-ubiquinone oxidoreductase (ETF-QO), proteins that transfer electrons from soluble mitochondrial flavoprotein dehydrogenases to the main respiratory chain. Cell lines from 11 severely affected GA2 infants were assayed for ETF by acy1 CoA:Q1 activity (using purified general acyl CoA dehydrogenase and ETF-QO as electron donor and acceptor), and for ETF-QO by comproportionation of ETF and by NADH:ETF reductase activity. All but one were deficient in ETF (5 patients; none with anomalies) or ETF-QO (5 patients; all with anomalies). The one that was not was from a girl with nonketotic hypoglycemia, a typical Zellweger facies, normal serum very long chain fatty acids, and glutaric, ethylmalonic, 3-hydroxyisovaleric and isovalerylglycine in urine who died at 6 months of age. Autopsy showed hypertrophic cardiomyopathy, moderate lipid deposition and canalicular stasis in liver, focal glomerular immaturity and cortical cysts in the kidney, and cysts in the cerebral cortex and basal ganglia. Glutaryl CoA dehydrogenase activity in fibroblasts was normal. This GA2 patient may have a defect in electron transfer between ETF-QO and complex III, and her phenotype may indicate interaction between peroxisomal and mitochondrial compartments.

A boy with glutaric acidemia had psychomotor retardation first noted at age 6 months, recurrent metabolic acidosis, and a progressive quadriparesis with choreoathetosis. He died at age 3 1/2 years. Cultured skin fibroblasts lacked glutaryl-CoA dehydrogenase activity. There was a biochemical, but not a clinical, response to dietary restriction of lysine and tryptophan. The caudate and putamen of the brain showed severe loss of nerve cells and fibers with proliferation of astrocytes, as well as markedly reduced gamma-aminobutyric acid and glutamate decarboxylase activity.

In Reply.— We thank Dr Hall and his associates for pointing out the typographical error in our formula for estimating propylene glycol concentration from osmolal gap.1 The correct formula is, as presumed by Hall et al, propylene glycol (mg/dL) = 47.5 + (osmolal gap x 9.2). It is important to remember that both our formula and that developed by Fligner et al2 are determined from linear regression analysis of experimentally derived data and are not theoretical calculations based on chemical properties of propylene glycol.

We have identified two brothers who appear to represent a previously undescribed disease. Their clinical problems include poor somatic growth (less than 3rd percentile), moderately severe psychomotor retardation, generalized spasticity, a non-paralytic esotropia, severe generalized osteoporosis resulting in pathologic fractures, and a “wizzened” facial appearance. At ages 18 months and 4 years there is no evidence of a degenerative course. There is no demonstrable renal, thyroid, parathyroid or nutritional problem. Histochemical studies of muscle demonstrate a strikingly dystrophic process. Routine and EM studies of bone show nonspecific osteoporosis. Gas chromatography-mass spectroscopy of urine indicates elevated glycerol concentrations in both patients. In a survey of an institutionalized, mentally retarded population, four patients were noted to excrete glycerol in their urine (Ann. Med. Exp. Fenn. 45:90, 1967). Three exhibited spasticity but no additional clinical information was presented. Our patients appear to represent a previously unrecognized, apparently genetic syndrome, characterized by psychomotor retardation, spasticity, dystrophic myopathy, osteoporosis, and glyceroluria.

Glutaric acid was elevated in plasma (0.1-0.6 mg %;normal = undetected), urine (5 gm/gm creatinine;normal=undetected),and CSF (0.25 mg %;normal=undetected) of two siblings, a 1½ year old girl and a 7½ year old boy. Both have a neurodegenerative disorder characterized by initial normalcy followed by progressive deterioration to opisthotonus and posturing. Recurrent metabolic acidemia was present in the male. One sibling has neither glutaric acidemia nor neurologic dysfunction, and the parents deny consanguinity. Glutaryl-CoA is an intermediate in the metabolism of L-lysine, L-tryptophan, and hydroxy-L-lysine, being further metabolized through glutaconyl-CoA to crotonyl-CoA. Oral administration of L-lysine augmented the glutaric aciduria; L-valine did not. Decreasing protein intake from 4.1 to 1.6 gm/kg/day decreased glutaric acid excretion from 5 to 2 gm/gm creat. The metabolism of glutaric acid-l,5-14C in peripheral leucocytes and cultured fibroblasts was normal. If inherited, transmission may be as an autosomal recessive trait; carriers cannot be differentiated easily from controls by lysine loading. It is speculated that (1) the disorder is due to a block at the level of glutaryl-CoA dehydrogenase, and (2) that CNS dysfunction may relate to inhibition by glutaric acid of transport or metabolism of glutamic acid.

821 INHERITED DEFICIENCY OF ETF DEHYDROGENASE (DH) IS A CAUSE OF GLUTARIC ACIDEMIA TYPE II (GA2) AND ETHYLMALONIC-ADIPIC ACIDEMIA (EMA)