Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
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Gene/Protein
Disease
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Target Concepts:
Gene/Protein
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Query: UMLS:C0348321 (
Haemophilus
)
15,372
document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)
A novel type of sulfotransferase, arylsulfate sulfotransferase [EC 2.8.2.22], was purified to homogeneity from
Haemophilus
K-12, a mouse intestinal bacterium. The purified enzyme (M(r) 290,000) is composed of four subunits (M(r) 70,000). The best donor substrate was 4-methylumbelliferyl sulfate, followed by beta-naphthyl sulfate, p-nitrophenyl sulfate (PNS), and alpha-naphthyl sulfate. The best acceptor substrate was alpha-naphthol, followed by phenol and resorcinol. The apparent Km for PNS using phenol as an acceptor and that for phenol and resorcinol. The apparent Km for PNS using phenol as an acceptor and that for phenol using PNS as a donor substrate were determined to be 0.095 and 0.71 mM, respectively. One of the reaction products, p-nitrophenol inhibited the enzyme noncompetitively with respect to PNS, but competitively with respect to alpha-naphthol. The Ki values of
PNP
for PNS and alpha-naphthol were 0.89 and 0.12 mM, respectively. The other reaction product, alpha-naphthyl sulfate, inhibited the enzyme competitively with respect to PNS, but non-competitively with respect to alpha-naphthol. The Ki values of alpha-naphthyl sulfate for PNS and for alpha-naphthol were 2.72 and 1.7 mM. These results suggest that the sulfate transfer reaction proceeds according to a ping pong bi bi mechanism.
...
PMID:Purification and reaction mechanism of arylsulfate sulfotransferase from Haemophilus K-12, a mouse intestinal bacterium. 857 95
NadR is a bifunctional enzyme that converts nicotinamide riboside (NR) into nicotinamide mononucleotide (NMN), which is then converted into nicotinamide adenine dinucleotide (NAD). Although a crystal structure of the enzyme from the Gram-negative bacterium
Haemophilus
influenzae
is known, structural understanding of its catalytic mechanism remains unclear. Here, we purified the NadR enzyme from
Lactococcus lactis
and established an assay to determine the combined activity of this bifunctional enzyme. The conversion of NR into NAD showed hyperbolic dependence on the NR concentration, but sigmoidal dependence on the ATP concentration. The apparent cooperativity for ATP may be explained because both reactions catalyzed by the bifunctional enzyme (phosphorylation of NR and adenylation of NMN) require ATP. The conversion of NMN into NAD followed simple Michaelis-Menten kinetics for NMN, but again with the sigmoidal dependence on the ATP concentration. In this case, the apparent cooperativity is unexpected since only a single ATP is used in the NMN adenylyltransferase catalyzed reaction. To determine the possible structural determinants of such cooperativity, we solved the crystal structure of NadR from
L. lactis
(NadR
Ll
). Co-crystallization with NAD, NR, NMN, ATP, and AMP-
PNP
revealed a 'sink' for adenine nucleotides in a location between two domains. This sink could be a regulatory site, or it may facilitate the channeling of substrates between the two domains.
...
PMID:Structural and Functional Characterization of NadR from
Lactococcus lactis
. 3233 17
