Study of heme oxygenase, a key enzyme in the iron acquisition

SOLDANO, ANABEL; CATALANO DUPUY, DANIELA L.; CECCARELLI, EDUARDO A.

Mendoza

Congreso; XLVIII Reunión Anual de la Sociedad Argentina de Investigación Bioquímica y Biología Molecular; 2012

Sociedad Argentina de Investigación Bioquímica y Biología Molecular

Leptospira interrogans, the pathogenic spirochete that caused leptospirosis, acquires its essential nutrient iron from the host hemoglobin during the infection. To scavenge the metal contained within the heme the bacterium utilizes an enzyme known as heme oxygenase (LepHO). Heme breakdown is a complex reaction that requires the input of seven electrons and three molecules of oxygen to release iron, biliverdin and carbon monoxide. Even though the mechanism of heme cleavage is broadly conserved between HOs from most organisms, the source of reducing equivalents is highly variable. So far there is no evidence of which proteins support the catalytic activity of LepHO by delivering the reducing power needed for the acquisition of iron. We have cloned and expressed the gene encoding LepHO in Escherichia coli cells and the recombinant product was purified by affinity chromatography as a soluble protein with a molecular weight of 26 kDa. The enzyme was able to bind its substrate heme with high affinity displaying a typical soret absorption peak of the complex at 402 nm. We also studied the catalytic system of heme degradation by optical absorption spectroscopy and we established the physiological electron-donating partner of LepHO. Our results suggest that the plastidic type ferredoxin-NADP+ reductase (LepFNR) found in this bacterium efficiently delivers the electrons needed by LepHO to oxidize heme into biliverdin.