Essential tryptophan residues of ribulose 1,5-bisphosphate carboxylase.

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dc.contributor.authorPurohit, U Sen_US
dc.contributor.authorBhagwat, A Sen_US
dc.date.accessioned1990-04-01en_US
dc.date.accessioned2009-05-27T09:30:03Z
dc.date.available1990-04-01en_US
dc.date.available2009-05-27T09:30:03Z
dc.date.issued1990-04-01en_US
dc.description.abstractRibulose 1,5-bisphosphate carboxylase [3-phospho-D-glyceratecarboxy-lyase (dimerizing), EC 4.1.1.39] is rapidly and irreversibly inactivated by micromolar concentrations of dimethyl (2-hydroxy-5-nitrobenzyl) sulphonium bromide (DMHNB), a tryptophan selective reagent, after reversible protection of the reactive sulphydryl groups. The inactivation followed pseudo-first-order reaction kinetics. Replots of the kinetic data indicated that no reversible enzyme-inhibitor complex was formed prior to irreversible modification. Kinetic analysis and the correlation of the spectral data at 410 nm with enzyme activity indicated that inactivation by DMHNB resulted from modification of on an average one tryptophan per 67 kDa combination of large and small subunits. Several competitive inhibitors and substrate RuBP offered strong protection against inhibition. The k1/2 (protection) for RuBP was 1.3 mM, indicating that the tryptophan residues may be located at or near the substrate binding site. Free and total sulphydryl groups were not affected by the reagent. The modified enzyme exhibited significantly reduced intrinsic fluorescence, indicating that the microenvironment of the tryptophans at the active site is significantly perturbed. Tryptic peptide profiles and CD spectral analyses suggested that inactivation may not be due to the extensive conformational changes in the enzyme molecule during modification.en_US
dc.description.affiliationMolecular Biology and Agriculture Division, Bhabha Atomic Research Centre, Trombay, Bombay, India.en_US
dc.identifier.citationPurohit US, Bhagwat AS. Essential tryptophan residues of ribulose 1,5-bisphosphate carboxylase. Indian Journal of Biochemistry & Biophysics. 1990 Apr; 27(2): 81-7en_US
dc.identifier.urihttps://imsear.searo.who.int/handle/123456789/27693
dc.language.isoengen_US
dc.source.urihttps://https://www.niscair.res.in/ScienceCommunication/ResearchJournals/rejour/ijbb/ijbb0.aspen_US
dc.subject.meshBinding Sitesen_US
dc.subject.meshRibulose-Bisphosphate Carboxylase --analysisen_US
dc.subject.meshSulfonium Compounds --pharmacologyen_US
dc.subject.meshTryptophan --analysisen_US
dc.titleEssential tryptophan residues of ribulose 1,5-bisphosphate carboxylase.en_US
dc.typeJournal Articleen_US
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