ExplorEnz: EC 6.3.4.21

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6.3.4.21

Accepted name:

nicotinate phosphoribosyltransferase

Reaction:

nicotinate + 5-phospho-α-D-ribose 1-diphosphate + ATP + H₂O = β-nicotinate D-ribonucleotide + diphosphate + ADP + phosphate

For diagram of NAD⁺ biosynthesis, click here

Other name(s):

niacin ribonucleotidase; nicotinic acid mononucleotide glycohydrolase; nicotinic acid mononucleotide pyrophosphorylase; nicotinic acid phosphoribosyltransferase; nicotinate-nucleotide:diphosphate phospho-α-D-ribosyltransferase

Systematic name:

5-phospho-α-D-ribose 1-diphosphate:nicotinate ligase (ADP, diphosphate-forming)

Comments:

The enzyme, which is involved in pyridine nucleotide recycling, can form β-nicotinate D-ribonucleotide and diphosphate from nicotinate and 5-phospho-α-D-ribose 1-diphosphate (PRPP) in the absence of ATP. However, when ATP is available the enzyme is phosphorylated resulting in a much lower K_m for nicotinate. The phospho-enzyme is hydrolysed during the transferase reaction, regenerating the low affinity form. The presence of ATP shifts the products/substrates equilibrium from 0.67 to 1100 [4].

Links to other databases:

BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 9030-26-6

References:

1.	Imsande, J. Pathway of diphosphopyridine nucleotide biosynthesis in Escherichia coli. J. Biol. Chem. 236 (1961) 1494–1497. [PMID: 13717628]
2.	Imsande, J. and Handler, P. Biosynthesis of diphosphopyridine nucleotide. III. Nicotinic acid mononucleotide pyrophosphorylase. J. Biol. Chem. 236 (1961) 525–530. [PMID: 13717627]
3.	Kosaka, A., Spivey, H.O. and Gholson, R.K. Nicotinate phosphoribosyltransferase of yeast. Purification and properties. J. Biol. Chem. 246 (1971) 3277–3283. [PMID: 4324895]
4.	Vinitsky, A. and Grubmeyer, C. A new paradigm for biochemical energy coupling. Salmonella typhimurium nicotinate phosphoribosyltransferase. J. Biol. Chem. 268 (1993) 26004–26010. [PMID: 7503993]

[EC 6.3.4.21 created 1961 as EC 2.4.2.11, transferred 2013 to EC 6.3.4.21]