Protocatechuate 3,4-dioxygenase. Inhibitor studies and mechanistic implications. 1977

L Que, and J D Lipscomb, and E Münck, and J M Wood

Protocatechuate 3,4-dioxygenase (EC 1.13.11.3) from Pseudomonas aeruginosa catalyzes the cleavage of 3,4-dihydroxybenzoate (protocatechuate) into beta-carboxy-cis,cis-muconate. The inhibition constants, Ki, of a series of substrate analogues were measured in order to assess the relative importance of the various functional groups on the substrate. Though important for binding, the carboxylate group is not essential for activity. Compounds with para hydroxy groups are better inhibitors than their meta isomers. Our studies of the enzyme-inhibitor complexes indicate that the 4-OH group of the substrate binds to the active-site iron. Taken together, Mössbauer, EPR, and kinetic data suggest a mechanism where substrate reaction with oxygen is preceded by metal activation of substrate.

UI MeSH Term Description Entries
D007700 Kinetics The rate dynamics in chemical or physical systems.
D008956 Models, Chemical Theoretical representations that simulate the behavior or activity of chemical processes or phenomena; includes the use of mathematical equations, computers, and other electronic equipment. Chemical Models,Chemical Model,Model, Chemical
D010105 Oxygenases Oxidases that specifically introduce DIOXYGEN-derived oxygen atoms into a variety of organic molecules. Oxygenase
D011520 Protocatechuate-3,4-Dioxygenase An enzyme that catalyzes the oxidation of protocatechuate to 3-carboxy-cis-cis-muconate in the presence of molecular oxygen. It contains ferric ion. EC 1.13.11.3. Protocatechuate 3,4 Dioxygenase
D004578 Electron Spin Resonance Spectroscopy A technique applicable to the wide variety of substances which exhibit paramagnetism because of the magnetic moments of unpaired electrons. The spectra are useful for detection and identification, for determination of electron structure, for study of interactions between molecules, and for measurement of nuclear spins and moments. (From McGraw-Hill Encyclopedia of Science and Technology, 7th edition) Electron nuclear double resonance (ENDOR) spectroscopy is a variant of the technique which can give enhanced resolution. Electron spin resonance analysis can now be used in vivo, including imaging applications such as MAGNETIC RESONANCE IMAGING. ENDOR,Electron Nuclear Double Resonance,Electron Paramagnetic Resonance,Paramagnetic Resonance,Electron Spin Resonance,Paramagnetic Resonance, Electron,Resonance, Electron Paramagnetic,Resonance, Electron Spin,Resonance, Paramagnetic
D013329 Structure-Activity Relationship The relationship between the chemical structure of a compound and its biological or pharmacological activity. Compounds are often classed together because they have structural characteristics in common including shape, size, stereochemical arrangement, and distribution of functional groups. Relationship, Structure-Activity,Relationships, Structure-Activity,Structure Activity Relationship,Structure-Activity Relationships

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