[Various kinetic and spectral-fluorescent properties of NADP-dependent malate dehydrogenase from bovine adrenal cortex cytoplasm].
Malate dehydrogenase from bovine adrenal cortex has been purified to homogeneity, using affinity chromatography on 2',5'-ADP-Sepharose 4B. The kinetic data do not contradict the consecutive mechanism of the reaction with the ordered addition of substrates: NADP binds first, then malate. The enzyme conformation initiated by NADP and malate binding is less thermostable. Malate dehydrogenase has intrinsic tryptophan fluorescence with the spectrum maximum at 335 +/- 1 nm, half-width of 50 +/- 1 nm and quantum yield of 0.08. The tryptophan residues belonging to class 1 (75%) and class 2 (25%) make the main contribution to the intrinsic fluorescence of malate. The binding of cofactors and substrates results in the quenching of enzyme fluorescence. The values of dissociation constants for malate dehydrogenase complexes with NADP (4 microM), with NADP . H (8 microM) and with pyruvate (2.5 mM) correlate with the corresponding values of Km. The shifts in pH of the medium induce changes in the fluorescence parameters which are probably related to conformational changes in the enzyme molecule. The changes in the fluorescence parameters correlate with the alterations of the malate dehydrogenase enzymatic activity.
D000302:Adrenal Cortex / Q000201:enzymology*; D000818:Animals; D002417:Cattle; D003593:Cytoplasm / Q000201:enzymology; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008291:Malate Dehydrogenase / Q000378:metabolism*; D009249:NADP / Q000378:metabolism; D013050:Spectrometry, Fluorescence
D009249:NADP; D008291:Malate Dehydrogenase; C031917:malate dehydrogenase (oxaloacetate-decarboxylating) (NADP+)
Nekotorye kineticheskie i spektral'no-fluorestsentnye svoĭstva NADP-zavisimoĭ malatdegidrogenazy iz tsitoplazmy kory nadpochechnikov byka.