Thiamin metabolism

Metabolism of Cofactors, Vitamins, and Other Substances Thiamin metabolism Riboflavin metabolism Vitamin B6 metabolism Nicotinate and nicotinamide metabolism... 

Hohmann S and Meacock PA (1998) Thiamin metabolism and thiamin diphosphate-dependent enzymes in the yeast Saccharomyces cerevisiae. genetic regulation. Bio-chimica et Biophysica Acta 1385, 201-19. 

Reggiani C, Patrini C, and Hindi G (1984) Nervous tissue thiamine metabolism in vivo. 1. Transport of thiamine and thiamine monophosphate from plasma to different brain regions of the rat. Brain Research 293,319-27. 

Laforenza U, Patrini C, Rindi G (1988) Distribution of thiamine, thiamine phosphates, and thiamine metabolizing enzymes in neuronal and gUal cell enriched fractions of rat brain. J Neurochem 51(3) 730-735... 

Pruritus is a frequent adverse effect after intrathecal administration, with an incidence of one-third with bupre-norphine (122) and diamorphine (123) and over 70% for both diamorphine and morphine (124,125). In one stndy the incidence of pruritns was higher with morphine than with methadone analgesia was also snperior (124). Pruritus has also been reported with intrathecal pethidine (meperidine). Treatment was not reported to be necessary. This effect is not reported to occnr after intrathecal beta-endorphin (126,127). The mechanism of prnritns is not well understood and has been attribnted to a distnr-bance of thiamine metabolism (128) and to a distnrbance of afferent inpnt at snpraspinal as well as at spinal receptor sites (129). 

To investigate thiamine metabolism in mammals, thiamine (Rf values 0.16, 0.04, and 0.03), urinary excretion of thiamine metabolites [thiochirome (Rf values 0.31, 0.28, and 0.33), thiazole (Rf values 0.85, 0.79, and 0.81), and 2-methyl-4-amino-pyrimidinecarboxylic acid (Rf values 0.42, 0.21, and 0.26)], and related compounds [pyrimidinesulfonic acid (Rf values 0.48, 0.39, and 0.46), a-hydroxyethylthiamine (Rf values 0.23, 0.09, and 0.06), A -methylnicotinamide (Rf values 0.31, 0.06, and 0.05)] were analyzed and identified by TLC on silica gel with acetonitrile-water (40 10 vol/vol) adjusted to a pH of 2.54, 4.03, and 7.85 with formic acid as solvents, respectively.Although A -methylnicotinamide and thio-chrome could not be separated in single-phase chromatography at pH 2.54, a second phase at right angle, with a pH 4.03 solvent, separated these quite clearly without affecting the resolution of the other compounds. 

Using radio-labeled thiamine probes, a study of thiamine metabolism at normal loads produced an estimated half-life of thiamine of 9.5 to 18.5 days, and showed a large number of breakdown products in the urine. Several of these urinary catabolites are shown in Figure 30-9. 

Ariaey-Nejad MR, Balaghi M, Baker EM, Sauberlich HE, Thiamin metabolism in man. Am J Clin Nutr 1970 23 764-78. 

TenA - enzyme in thiamine metabolism [B], [A] 39 Cloned from 6. subtilis, enzyme assay 42... 

Neal, R.A., and Pearson, W.N., 1964. Studies of thiamine metabolism in the Rat. I. Metabolic products found in urine. Journal of Nutrition. 83 343-350. 

Thiamine is metabolized to TPP by thiamine pyrophosphokinase (EC 2.1.62) in animal cells including red and white blood cells. This enzyme is also present in plants, yeast, and a bacterium (Paracoccus denitrificans) (7). However, in some bacteria, for example in Escherichia coli, thiamine is metabolized to TPP by a two-step reaction catalyzed by thiamine kinase (EC 2.7.1.89) and TMP kinase (EC 2.7.4.10). Thiamine pyrophosphate is further metabolized to TI P in yeast, animal tissues, and human red blood cells. Evidence has been obtained which indicates that cytosolic adenylate kinase (EC 2.7.4.3) catalyzes TIP synthesis from TPP in vitro (8) and in vivo (3). The enzyme system involved in thiamine metabolism to TTP in human red blood cells was recently identified, purified, and reconstituted (9). 

Y Egi, S Koyama, T Shioda, K Yamada, T Kawasaki. Identification, purification and reconstitution of thiamin metabolizing enzymes in human red blood cells. Biochim... 

The active process of absorption is impaired by ethyl alcohol. For example, 55% of a 5 mg dose of orally administered, labeled thiamin was recovered over 72 h in healthy adults, but this was reduced by 25-40% if they were previously given 1.5-2 g alcohol/kg. In people with fatty livers who had previously been abusing alcohol, mean thiamin absorption was reduced by 60%. However, the passive absorption of thiamin is not inhibited by alcohol, nor does it block entry of thiamin into the liver or interfere with thiamin metabolism in the tissues. Absorption of thiamin may also be reduced by gastrointestinal disturbances, such as vomiting and diarrhea, ulcerative colitis, and neoplasia, and in patients with hepatic disease and achlorhydria. 

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