Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0348321 (Haemophilus)
 15,372 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The cloning and expression of the Haemophilus influenzae gene, nanA, for the putative N-acetylneuraminate lyase enzyme, also known as N-acetylneuraminic acid aldolase or sialic acid aldolase, are reported. The gene was isolated from ATCC type strain 49247 and cloned into the Escherichia coli expression vector pKKtac, which contained the strong tac promoter. Gene expression was compared with the homologous E. coli npl gene coding for the lyase. Purification protocols for the products of the nanA and npl genes are presented. Activity analysis showed that the nanA gene product is a sialic acid aldolase with more than threefold greater specific activity (6.9 IU/mg) than the enzyme from E. coli (</=2 IU/mg). A method for the provision of lyase orthorhombic crystals is reported. These crystals diffract to better than 2.0 A, which paves the way to the solution of the enzyme's three-dimensional structure.
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PMID:Expression in Escherichia coli of the putative N-acetylneuraminate lyase gene (nanA) from Haemophilus influenzae: overproduction, purification, and crystallization. 953 96

The N-acetylneuraminate lyase (NAL) sub-family of (beta/alpha)(8) enzymes share a common catalytic step but catalyse reactions in different biological pathways. Known examples include NAL, dihydrodipicolinate synthetase (DHDPS), d-5-keto-4-deoxyglucarate dehydratase, 2-keto-3-deoxygluconate aldolase, trans-o-hydroxybenzylidenepyruvate hydrolase-aldolase and trans-2'-carboxybenzalpyruvate hydratase-aldolase. Little is known about the way in which the three-dimensional structure of the respective active sites are modulated across the sub-family to achieve cognate substrate recognition. We present here the structure of Haemophilus influenzae NAL determined by X-ray crystallography to a maximum resolution of 1.60 A, in native form and in complex with three substrate analogues (sialic acid alditol, 4-deoxy-sialic acid and 4-oxo-sialic acid). These structures reveal for the first time the mode of binding of the complete substrate in the NAL active site. On the basis of the above structures, that of substrate-complexed DHDPS and sequence comparison across the sub-family we are able to propose a unified model for active site modulation. The model is one of economy, allowing wherever appropriate the retention or relocation of residues associated with binding common substrate substituent groups. Our structures also suggest a role for the strictly conserved tyrosine residue found in all active sites of the sub-family, namely that it mediates proton abstraction by the alpha-keto acid carboxylate in a substrate-assisted catalytic reaction pathway.
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PMID:Active site modulation in the N-acetylneuraminate lyase sub-family as revealed by the structure of the inhibitor-complexed Haemophilus influenzae enzyme. 1103 Nov 17