Poster Presentation 1B-50

NAD⁺-Dependent Dihydro-diol-dehydrogenase: Possible Participant in Biodegradation of Aromatic Hydrocarbons in Mucor circinelloides.

Roberto Zazueta-Sandoval,* Vanesa Zazueta Novoa, José Manuel Zamudio Arroyo, Maria de los Angeles Herrera Cano, Arelí Durón Castellanos, Hortensia Silva Jimenez

and Eduardo Peña Cabrera

IIBE. Facultad de Química

Universidad de Guanajuato

Noria Alta s/n CP 36050

Guanajuato, Gto., Mexico

Phone: (473)732 0006 ext. 8148

Fax: ext. 8153

E-mail: zazueta@ quijote.ugto.mx

For most microorganisms growing under normal conditions, a very small amount of cellular oxygen is derived from molecular O₂. Instead, it is derived from water, carbon dioxide or other organic compounds. However, for microorganisms growing in highly reduced substrates (e.g. hydrocarbons), the primary attack on the substrate is usually via an oxygenase reaction which involves the incorporation of molecular O₂ into the substrate molecules.

The ability of oxygenases to incorporate oxygen into organic compounds is very important because many hydrophobic pollutants such as polycyclic aromatic hydrocarbons are high in C and H content and low in O content. So, through the action of oxygenases, the hydrophobic organic compounds become more water soluble and can be metabolized or broken down by a larger number of other microorganisms. The second step in this pathway is catalyzation by dihydrodiol-dehydrogenase to make the di-hydrodiol derivate, followed by the cathecol pathway. These enzymes participate in the oxidative metabolism of a wide variety of chemicals of pharmaceutical, agricultural and environmental significance. Some of the most widely recognized substrates for these classes of enzymes are produced from the aromatic hydrocarbons of both endobiotic and xenobiotic sources.

In this work we describe some biophysical properties of the alcohol dehydrogenase activities with emphasis on the dihydrodiol dehydrogenase activity, the second enzyme in the metabolic pathway of aerobic hydrocarbon degradation present in cell free extracts of the microorganism.

Initially, we developed a spectrophotometric method to measure the dehydrogenase activity, using several variations of a described method to measure the activity of horse liver alcohol dehydrogenase. Also we make other variations to get the zymograms of the alcohol dehydrogenase activities and particularly dihydrodiol-dehydrogenase activity. We also prepare by chemical synthesis the compound phenantrenediol to use as substrate.