A 5-year-old boy, excreting large amounts of 2-hydroxyglutaric acid in the urine (3.3-7.6 mmol/l), is described. The patient presented with psychomotor retardation and dystrophy. His skeletal age was delayed. The EEG was not well differentiated; it resembled that observed in 2-year-old children. There was a severe anaemia, which reacted well to iron supplements. The 2-hydroxyglutaric acid was found to have the L-configuration, as analysed by capillary gas chromatography of the O-acetylated di-(-)-2-butyl ester derivative. The relation of L-2-hydroxyglutarate excretion to known metabolic pathways is discussed.

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Morphology and structural integrity of fungal cells depend on cell wall polysaccharides. The chemical structure and biosynthesis of two types of these polysaccharides, chitin and (1-->3)-beta-glucan, have been studied extensively, whereas little is known about alpha-glucan. Here we describe the chemical structure of alpha-glucan isolated from wild-type and mutant cell walls of the fission yeast Schizosaccharomyces pombe. Wild-type alpha-glucan was found to consist of a single population of linear glucose polymers, approximately 260 residues in length. These glucose polymers were composed of two interconnected linear chains, each consisting of approximately 120 (1-->3)-linked alpha-d-glucose residues and some (1-->4)-linked alpha-D-glucose residues at the reducing end. By contrast, alpha-glucan of an alpha-glucan synthase mutant with an aberrant cell morphology and reduced alpha-glucan levels consisted of a single chain only. We propose that alpha-glucan biosynthesis involves an ordered series of events, whereby two alpha-glucan chains are coupled to create mature cell wall alpha-glucan. This mature form of cell wall alpha-glucan is essential for fission-yeast morphogenesis.

Lactobacillus reuteri LB 121 cells growing on sucrose synthesize large amounts of a glucan (d-glucose) and a fructan (d-fructose) with molecular masses of 3,500 and 150 kDa, respectively. Methylation studies and 13C or1H nuclear magnetic resonance analysis showed that the glucan has a unique structure consisting of terminal, 4-substituted, 6-substituted, and 4,6-disubstituted α-glucose in a molar ratio of 1.1:2.7:1.5:1.0. The fructan was identified as a (2→6)-β-d-fructofuranan or levan, the first example of levan synthesis by a Lactobacillus species. Strain LB 121 possesses glucansucrase and levansucrase enzymes that occur in a cell-associated and a cell-free state after growth on sucrose, raffinose, or maltose but remain cell associated during growth on glucose. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of sucrose culture supernatants, followed by staining of gels for polysaccharide synthesizing activity with sucrose as a substrate, revealed the presence of a single glucansucrase protein of 146 kDa. Growth of strain LB 121 in chemostat cultures resulted in rapid accumulation of spontaneous exopolysaccharide-negative mutants that had lost both glucansucrase and levansucrase (e.g., strain K-24). Mutants lacking all levansucrase activity specifically emerged following a pH shiftdown (e.g., strain 35-5). Strain 35-5 still possessed glucansucrase and synthesized wild-type glucan.