Neurologically normal development of a patient with severe methionine adenosyltransferase I/III deficiency after continuing dietary methionine restriction

Background

There is not much information on established standard therapy for patients with severe methionine adenosyltransferase (MAT) I/III deficiency.

Case presentation

We report a boy with MAT I/III deficiency, in whom plasma methionine and total homocysteine, and urinary homocystine were elevated. Molecular genetic studies showed him to have novel compound heterozygous mutations of the MAT1A gene: c.191T>A (p.M64K) and c.589delC (p.P197LfsX26). A low methionine milk diet was started at 31 days of age, and during continuing dietary methionine restriction plasma methionine levels have been maintained at less than 750 μmol/L. He is now 5 years old, and has had entirely normal physical growth and psychomotor development.

Conclusions

Although some severely MAT I/III deficient patients have developed neurologic abnormalities, we report here the case of a boy who has remained neurologically and otherwise normal for 5 years during methionine restriction, suggesting that perhaps such management, started in early infancy, may help prevent neurological complications.     

Interactions of bacterial flagellar chaperone–substrate complexes with FlhA contribute to co‐ordinating assembly of the flagellar filament

Assembly of the bacterial flagellar filament is strictly sequential; the junction proteins, FlgK and FlgL, are assembled at the distal end of the hook prior to the FliD cap, which supports assembly of as many as 30 000 FliC molecules into the filament. Export of these proteins requires assistance of flagellar chaperones: FlgN for FlgK and FlgL, FliT for FliD and FliS for FliC. The C‐terminal cytoplasmic domain of FlhA (FlhA_C), a membrane component of the export apparatus, provides a binding‐site for these chaperone–substrate complexes but it remains unknown how it co‐ordinates flagellar protein export. Here, we report that the highly conserved hydrophobic dimple of FlhA_C is involved in the export of FlgK, FlgL, FliD and FliC but not in proteins responsible for the structure and assembly of the hook, and that the binding affinity of FlhA_C for the FlgN/FlgK complex is slightly higher than that for the FliT/FliD complex and about 14‐fold higher than that for the FliS/FliC complex, leading to the proposal that the different binding affinities of FlhA_C for these chaperone/substrate complexes may confer an advantage for the efficient formation of the junction and cap structures at the tip of the hook prior to filament formation.     

Production of l-Tryptophan by Azaserine-resistant Mutants of Brevibacterium flavum

Azaserine-resistant mutants derived from a 5-fluorotryptophan-resistant, l-tryptophan-producing mutant of Brevibacterium flavum, accumulated 10.3 g/liter of l-tryptophan at maximum. The production increased to 11.4 g/liter when l-serine was added. In the mutant, only anthranilate synthase among enzymes of the tryptophan-specific bio synthetic pathway increased in activity to a 2-fold higher level than that in the parent strain, No. 187. Sensitivity of anthranilate synthase to the feedback inhibition was not altered by the mutation. Activity of 3-deoxy-d-arabino-heptulosonate 7-phosphate synthase, the first common enzyme for aromatic amino acid biosynthesis, also increased 2.7-fold and was less sensitive to the feedback inhibition by phenylalanine and tyrosine. Tryptophan transport activity in strain A-100 was similar as that in the parent. Azaserine inhibited anthranilate synthase activity by 50% at 0.075 mm. The inhibition was of a mixed type with respect to both the two substrates. Anthranilate synthase of strain A-100 was inhibited in a similar manner to that of the parent.     

Phase Changes in Amylose–Butanol Complex Solution

The phase change for an amylose–butanol complex solution in 10% of dimethylsulfoxide was investigated as a function of temperature. The phase change was determined with measurements of the turbidity, fluorescent depolarization, and viscosity. The phase diagram obtained was qualitatively similar to that for an amylose solution. From the result, the change in solution phase for the amylose–butanol complex is suggested to be similar to that for amylose, i.e., when the solution cools from a higher temperature, amylose molecules in the complex solution change the conformation from a random coil to an interrupted helix, and then separate into two phases. Coacervate particles resulting from the phase separation coalesce with each other to yield precipitates.

An adsorption of uranine on amylose was studied to ascertain its relationship with the fluorescent depolarization method used for detecting phase changes in solution. The result showed that uranine was adsorbed on amylose chains but not on the amylose–butanol complex.     

Mechanism of the Acid-catalyzed Rearrangement of Thionocarbamates

A mixture of two thionocarbamates was subjected to the acid-catalyzed rearrangement. A sample of the reaction mixture was analyzed by glpc and resolved into four components. From the cross-over result, it has been concluded that the acid-catalyzed rearrangement of alkyl thionocarbamates into the isomeric thiolcarbamates proceeds by an intermolecular alkylating mechanism. This conclusion was supported by the detection of a transalkylated intermediate.     

Tetradecane 1,14-Dicarboxylic Acid Production from n-Hexadecane by Candida cloacae

The better condition of cultivation for tetradecane 1,14-dicarboxylic acid (DC-16) production from n-hexadecane (n-C₁₆) by Candida cloacae MR-12 was investigated by using acetic acid as carbon source for the growth. In general, the condition suitable for the growth was also favorable for the production of DC-16. The change of pH during cultivation, the use of NaOH solution as pH controlling agent after pH-change and the addition of antifoam stimulated the production of DC-16.

Under the optimum conditions where the culture medium contained 15% (v/v) n-C₁₆, 1.4% (w/v) acetic acid, inorganic salts and growth factors, and pH was changed from 6.5 to 7.75 at 16 hr after the inoculation, the highest level of DC-16 production was attained after about 72 hr cultivation and the amount of the product accumulated was 61.5 g per liter of the medium.

When a mixture of various n-alkanes was used as starting material, DCs corresponding to the respective n-alkanes were produced as mixture.     

Microbial Production of l-Threonine

The growth of Brevibacterium flavum No. 2247 was inhibited over 90% at a concentration above 1 mg/ml of α-amino-β-hydroxyvaleric acid, a threonine analogue, and the inhibition was reversed by the addition of l-threonine, and to lesser extent by l-leucine, l-isoleucine, l-valine and l-homoserine. l-Methionine stimulated the inhibition. Several mutants resistant to the analogue produced l-threonine in the growing cultures. The percentage of l-threonine producer in the resistant mutants depended on the concentration of the analogue, to which they were resistant. The best producer, strain B-183, was isolated from resistant strains selected on a medium containing 5 mg/ml of the analogue. Mutants resistant to 8 mg/ml of the analogue was derived from strain B-183 by the treatment with mutagen, N-methyl-N’-nitro-N-nitrosoguanidine. Among the mutants obtained, strain BB-82 produced 13.5 g/liter of l-threonine, 30% more than did the parental strain. Among the resistant mutants obtained from Corynebacterium acetoacidophilum No. 410, strain C-553 produced 6.1 g/liter of l-threonine. Several amino acids other than l-threonine were also accumulated, and these accumulations of amino acids were discussed from the view of regulation mechanism of l-threonine biosynthesis.     

Polarographic Studies on Fat-soluble Vitamins in Nonaqueous Media

Polarographic reduction-wave of vitamin K₃ showed two inflexions in acetonitrile as solvent. The first step inflexion is caused by reduction of quinone to semiquinone stabilized as anion free-radical in acetonitrile, and the second by reduction of semiquinone to hydro-quinone dianion. With small addition of water, the dismutation of semiquinone is accelerated and the reduction-wave becomes only one step inflexion. The reduction-wave in acetonitrile is controlled by diffusion. The total wave-h eight is strictly proportional to the concentration of vitamin K₃. The measurement is not disturbed by coexistent fatty substances.     

The Piperaceae Amides I: Structure of Pipercide,A New Insecticidal Amide from Piper nigrum L.

It was evidenced that mutagenic principles in tryptophan pyrolysate, 3-amino-1,4-dimethyl-5H pyrido(4,3-b) indole and 3-amino-1-methyl-5H pyrido(4,3-b) indole (abbreviated as Trp-P-1 and Trp-P-2, respectively) bind to DNA without activation by rat liver microsomes. The bindings of Trp-P-1 and Trp-P-2 were not random and did not introduce strand scissions into DNA. Trp-P-1 bound more easily than Trp-P-2. The bindings of these mutagenic principles to DNA were concluded by using negatively superhelical simian virus 40 (SV40) DNA from following experimental data. (1) The intensity of ethidium bromide (EtBr)-DNA fluorescence by illumination with UV light and the electrophoretic mobility of superhelical DNA in agarose gel decreased as a function of the amounts of Trp-P-1 and Trp-P-2. (2) In vitro RNA synthesis catalyzed by Escherichia coli DNA-dependent RNA polymerase and nick-translation catalyzed by Escherichia coli DNA polymerase I (Kornberg enzyme) were inhibited significantly on DNA treated with Trp-P-1 and Trp-P-2. (3) The negative superhelicity of SV40 DNA introduces unpaired regions into DNA. These regions can be cleaved by single-strand-specific S1 endonuclease to generate unit length linear duplex molecules. It was found that this S1-sensitivity of DNA decreased by treatment with Trp-P-1. (4) The cleavage patterns of Trp-P-1 treated DNA with five restriction endonucleases were investigated. The protection of the cleavage site by the drug was observed against HincII, HindIII and EcoRII, whereas not against HaeIII and HinfI. These results show that the binding of Trp-P-1 to DNA is not random. Identical results were also obtained in Trp-P-2.

However, the bindings of Trp-P-1 and Trp-P-2 were not so tight, and phenol extraction of the complex dissociated these drugs from DNA.     

Production of Nucleic Acid-Related Substances by Fermentative Processes

An adenine-requiring mutant (KY7208) of Brevibacterium ammoniagenes ATTC 6872 was found to accumulate an appreciable quantity of IMP and hypoxanthine in the culture liquid.

Crystalline IMP was isolated from culture broth of KY7208 by the use of ion-exchange columns. The preparation obtained was definitely identified as 5′-IMP, based on the results on paperchromatography, UV and IR absorption spectra, and analyses of its hydrolysates.

Growth responses of this mutant were demonstrated to adenine and adenosine, but not to 5′-AMP, 3′-AMP and 5′-AMP.

Over 5 mg of IMP per ml of broth were produced by the organism in natural medium consisting of glucose, yeast extract, urea, high concentrations of phosphate and magnesim salts, and others. The chemical changes showed that hypoxanthine first accumulated in the earlier stage of fermentation, and IMP synthesis then took place with the disappearance of hypoxanthine in the later stage of fermentation.