Linked Life Data

19501038

Source:http://linkedlifedata.com/resource/pubmed/id/19501038

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
2
pubmed:dateCreated
2009-7-14
pubmed:abstractText
O-Acetylserine sulfhydrylase (OASS) is a pyridoxal 5'-phosphate (PLP)-dependent enzyme that catalyzes the conversion of O-acetylserine and bisulfide to l-cysteine and acetate in bacteria and higher plants. Enteric bacteria have two isozymes of OASS, A and B, produced under aerobic and anaerobic growth conditions, respectively, with different substrate specificities. The (31)P chemical shift of the internal and external Schiff bases of PLP in OASS-B are further downfield compared to OASS-A, suggesting a tighter binding of the cofactor in the B-isozyme. The chemical shift of the internal Schiff base (ISB) of OASS-B is 6.2 ppm, the highest value reported for the ISB of a PLP-dependent enzyme. Considering the similarity in the binding sites of the PLP cofactor for both isozymes, torsional strain of the C5-C5' bond (O4'-C5'-C5-C4) of the Schiff base is proposed to contribute to the further downfield shift. The chemical shift of the lanthionine external Schiff base (ESB) of OASS-B is 6.0 ppm, upfield from that of unliganded OASS-B, while that of serine ESB is 6.3 ppm. Changes in chemical shift suggest the torsional strain of PLP changes as the reaction proceeds. The apoenzyme of OASS-B was prepared using hydroxylamine as the resolving reagent. Apoenzyme was reconstituted to holoenzyme by addition of PLP. Reconstitution is pseudo-first order and exhibits a final maximum recovery of 81.4%. The apoenzyme shows no visible absorbance, while the reconstituted enzyme has a UV-visible spectrum that is nearly identical to that of the holoenzyme. Steady-state fluorescence spectra gave tryptophan emission of the apoenzyme that is 3.3-fold higher than the emission of either the native or reconstituted enzyme, suggesting that PLP is a potent quencher of tryptophan emission.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Jul
pubmed:issn
1096-0384
pubmed:author
pubmed:issnType
Electronic
pubmed:day
15
pubmed:volume
487
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
85-90
pubmed:meshHeading
pubmed:year
2009
pubmed:articleTitle
(31)P NMR studies of O-acetylserine sulfhydrylase-B from Salmonella typhimurium.
pubmed:affiliation
Department of Chemistry and Biochemistry, University of Oklahoma, Norman, OK 73019, USA.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't