Biosynthesis pyrophosphorylase

This enzyme [EC 2.4.2.18], also referred to as phospho-ribosyl-anthranilate pyrophosphorylase, catalyzes the reaction of anthranilate with phosphoribosylpyrophos-phate to produce A-5 -phosphoribosylanthranilate and pyrophosphate. In certain species, this enzyme is part of a multifunctional protein, together with one or more other components of the system for the biosynthesis of tryptophan (i.e., indole-3-glycerol-phosphate synthase, anthranilate synthase, tryptophan synthase, and phos-phoribosylanthranilate isomerase). 

In contrast to animals, bacteria such as E. coli synthesize glycogen via ADP-glucose rather than UDP-glucose.88 ADP-glucose is also the glucosyl donor for synthesis of starch in plants. The first step in the biosynthesis (Eq. 20-18) is catalyzed by the enzyme ADP-glucose pyrophosphorylase (named for the reverse reaction). 

Fig. 6.—Hypothetical Model for the Biosynthesis of Cellulose.184 [Numbers refer to reactions catalyzed by the following enzymes 1, invertase (EC 3.2.1.26) 2, sucrose synthetase 3, hexokinase (EC 2.7.1.1) 4, phosphoglucomutase (EC 2.7.5.1) 5, UDP-glucose pyrophosphorylase and 6, 7, and 8, hypothetical reactions in the pathway to cellulose.]...

Furlong, C. E., and Preiss, J. 1969. Biosynthesis of bacterial glycogen synthesis. VII. Purification and properties of adenosine diphosphoglucose pyrophosphorylase of Rhodospirillum rubrum. J. Biol. Chem. 244,2539-2548. 

Greenberg, E., Preiss, J. E., VanBoldrick, M., and Preiss, J. 1983. Biosynthesis of bacterial glycogen Activator specificity of the ADPglucose pyrophosphorylase of Rhodopseudomo-nads. Arch. Biochem. Biophys. 220, 594-604. 

Sanwal, G. G., Greenberg, E., Hardie, J., Cameron, E., and Preiss, J. 1968. Regulation of starch biosynthesis in plant leaves Activation and inhibition of ADPglucose Pyrophosphorylase. Plant Physiol. 43, 417-427. 

Weber, H., Heim, U., Borisjuk, L., and Wobus, U. 1995. Cell-type specific, coordinate expression of two ADPglucose pyrophosphorylase genes in relation to starch biosynthesis during seed development in Vicia faba L. Planta 195, 352-361. 

Hill MA, Kaufmann K, Otero J, Preiss J. Biosynthesis of bacterial glycogen mutagenesis of a catal)4ic site residue of ADPglucose pyrophosphorylase from Escherichia coli. J. Biol. Chem. 1991 266 12455-12460. 

In higher mammals, riboflavin is absorbed readily from the intestines and distributed to all tis.sues. It is the precursor in the biosynthesis of the cocnzyme.s flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD). The metabolic functions of this vitamin involve these Iwocoenzymes. which participate in numerous vital oxidation-reduction proces.ses. FMN (riboflavin 5 -phosphate) is produced from the vitamin and ATP by flavokinasc catalysis. This step con be inhibited by phcnothiazincs and the tricyclic antidepressants. FAD originates from an FMN and ATP reaction that involves reversible dinucicotide formation catalyzed by flavin nucleotide pyrophosphorylase. The.se coenzymes function in combination with several enzymes as coenzyme-en-zyme complexes, often characterized as, flavoproteins. 

Vitamin Bi is an essential co-factor for several enzymes of carbohydrate metabolism such as transketolase, pyruvate dehydrogenase (PDH), pyruvate decarboxylase and a-ketoglutarate dehydrogenase. To become the active co-factor thiamin pyrophosphate (TPP), thiamin has to be salvaged by thiamin pyrophosphokinase or synthesized de novo. In Escherichia coli and Saccharomyces cerevisiae thiamin biosynthesis proceeds via two branches that have to be combined. In the pyrimidine branch, 4-amino-5-hydroxymethy-2-methylpyrimidine (PIMP) is phosphorylated to 4-amino-2-methyl-5-hydroxymethyl pyrimidine diphosphate (PIMP-PP) by the enzyme HMP/HMP-P kinase (ThiD) however, the step can also be catalyzed by pyridoxine kinase (PdxK), an enzyme also responsible for the activation of vitamin B6 (see below). The second precursor of thiamin biosynthesis, 5-(2-hydroxyethyl)-4-methylthiazole (THZ), is activated by THZ kinase (ThiM) to 4-methyl-5-(2-phosphoethyl)-thiazole (THZ-P), and then the thia-zole and pyrimidine moieties, HMP-PP and THZ-P, are combined to form thiamin phosphate (ThiP) by thiamin phosphate synthase (ThiE). The final step, pyrophosphorylation, yields TPP and is carried out by thiamin pyrophosphorylase (TPK). 

The alginate pathway and the activities of the alginate enzymes overlap with a few other metabolic endpoints. The committed step in alginate biosynthesis is the formation of GDP-mannuronate. GDP-mannose is the precursor of GDP-rhamnose, a constituent of the A-band in lipopolysaccharide (EPS). The GDP-mannose that is required for A-band EPS biosynthesis is formed by the action of phosphomannose isomerase (PMI)/GDP-mannose pyrophosphorylase (GMP) activities that are separate from those used in... 

Kim, Y.S. Nosaka, K. Downs, D.M. Kwak, J.M. Park, D. Chung, I.K. Nam, H.G. A Brassica cDNA clone encoding a bifunctional hydroxymethylpyrimidine kinase/thiamin-phosphate pyrophosphorylase involved in thiamin biosynthesis. Plant Mol. Biol., 37, 955-966 (1998)... 

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