Cysteine-glucose mixture

Pyruvaldehyde is a liquid at room temperature and boils at 72°C, thus when cysteine-pyruvaldehyde mixture was heated at 80°C, the components are in solution and flavor notes reminiscent of Japanese rice cracker developed. As reaction temperatures increased gradually other flavor notes developed. In the case of cysteine-glucose system, no reaction took place until the reaction temperature reached 130°C. The flavor of cysteine-glucose was comparable to that of cysteine-pyruvaldehde at 160°C, with one exception, the glucose system had a sweet note. As temperature increased the flavor impression of both systems increased in similarity. The volatile compounds produced at 160°C in the presence of pyruvaldehyde were different from those in presence of glucose. While thiazole and thazolines were absent in the volatiles of cysteine-glucose, cysteine-pyruvaldehyde volatiles were devoid of pyridines, picolines and furans (24). 

Dawes and Edwards (1966) isolated it from the volatiles obtained by heating a mixture of D-fructose and glycine or L-3-phenylalanine. Wang et al. (1969) presented a model reaction in which the product of condensation of pyruvaldehyde with any amino acid degraded by a Strecker reaction can form an aminoketone which by subsequent steps of self-condensation and oxidation formed 2,5-dimethylpyrazine (Wang et al., 1969 Manley et al., 1974). It was found in a heated cysteine/glucose model system (Sheldon et al., 1986). 

Male rats used for the perfusion experiments were maintained under established conditions and were fasted 16-24 hours prior to surgery as previously described (35). In the first series of studies the luminal perfusate was at pH 4.2. This perfusate consisted of M199 tissue culture medium which contained a variety of amino acids, vitamins and minerals plus glucose. The perfusate was supplemented (at 110 umolar) with L-histidine HCl, L-cysteine, L-methionine, L-tryptophan, 2-picolinic acid, citric acid, or reduced glutathione. The mixture was Infused into the lumen at 0.39 ml per min for 20 min and 0.10 ml per min for the final 40 min of the experiments. The small Intestine was then removed and mucosal... 

The ATP produced is measured by hexokinase (HK)/ glucose-6-phosphate dehydrogenase (G6PD) coupled reactions that ultimately convert NADP to NADPH, which is monitored spectrophotometricaUy. Oliver first reported this method that RosaUd also described with the improvement of adding AMP to inhibit adenylate kinase (AK) and cysteine to activate CK. Subsequently, Szasz and colleagues optimized the assay by adding N-acetylcysteine to activate CK, EDTA to bind Ca and to increase the stability of the reaction mixture, and adenosine pentaphosphate (ApsA) in addition to AMP to inhibit AK. A reference method based on this previous experience was developed by the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) it was modified recently to produce a reference procedure for the measurement of CK at 37 °C. ... 

A mixture of 1 M of each amino acid (glycine, isoleucine, lysine, arginine, histidine, glutamic acid, serine, cysteine or phenylalanine) with 2 M glucose in 0.2 M NaHC03 solution was heated at 100°C for 7 h and then dialyzed for 3 days at 4°C, with renewing the... 

Aliquots (75 pi of 1% solution) of the supernatants of the enzymic hydrolysates of starches were injected into a water-jacketed column (50 x 1.0 cm i.d.) packed with Biogel P2 (400 mesh particle size) and maintained at 60 C. The mobile phase was 0.1 M sodium chloride with a flow rate of 0.16 mL/min. The column eluent was continuously monitored using an automated L-cysteine sulfuric acid assay. The system was standardized by injecting a mixture of glucose and malto-oligosaccharides of known composition. 

In contrast to the system of Shimura et al. (1964), intact protoplasts of strain 10716 require six amino acids for production of bacitracin and, for maximal yield, glucose is needed. Disrupted protoplasts are unable to synthesize the antibiotic (Snoke, 1961). With protoplasts, the six needed amino acids are L-cysteine, L-isoleucine, L-leucine, L-histidine, L-ornithine, and L-asparagine. Neither D-orni-thine nor D-asparagine can be utihzed directly and D-phenylalanine inhibits formation of bacitracin in the absence of L-phenylalanine. A peptide factor in soybean was found to be stimulatory for synthesis of bacitracin by whole cells provided that D-phenylalanine is present in the reaction mixture (Snoke, i960, 1961). In the absence of the D-amino acid, the peptide factor is inactive. 

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