Linked Life Data

20879713

Source:http://linkedlifedata.com/resource/pubmed/id/20879713

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
44
pubmed:dateCreated
2011-4-19
pubmed:abstractText
Nicotinamidase/pyrazinamidase (PncA) is involved in the NAD+ salvage pathway of Mycobacterium tuberculosis and other bacteria. In addition to hydrolyzing nicotinamide into nicotinic acid, PncA also hydrolyzes the prodrug pyrazinamide to generate the active form of the drug, pyrazinoic acid, which is an essential component of the multidrug treatment of TB. A coupled enzymatic activity assay has been developed for PncA that allows for the spectroscopic observation of enzyme activity. The enzyme activity was essentially pH-independent under the conditions tested; however, the measurement of the pH dependence of iodoacetamide alkylation revealed a pK value of 6.6 for the active site cysteine. Solvent deuterium kinetic isotope effects revealed an inverse value for kcat of 0.64, reconfirming the involvement of a thiol group in the mechanism. A mechanism is proposed for PncA catalysis that is similar to the mechanisms proposed for members of the nitrilase superfamily, in which nucleophilic attack by the active site cysteine generates a tetrahedral intermediate that collapses with the loss of ammonia and subsequent hydrolysis of the thioester bond by water completes the cycle. An inhibitor screen identified the competitive inhibitor 3-pyridine carboxaldehyde with a Ki of 290 nM. Additionally, pyrazinecarbonitrile was found to be an irreversible inactivator of PncA, with a kinact/KI of 975 M(?1) s(?1).
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Nov
pubmed:issn
1520-4995
pubmed:author
pubmed:issnType
Electronic
pubmed:day
9
pubmed:volume
49
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
9613-9
pubmed:dateRevised
2011-11-14
pubmed:meshHeading
pubmed:year
2010
pubmed:articleTitle
Kinetics and inhibition of nicotinamidase from Mycobacterium tuberculosis.
pubmed:affiliation
Department of Biochemistry, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
pubmed:publicationType
Journal Article, Research Support, N.I.H., Extramural