Renalase : a new human flavoprotein possibly involved in the regulation of cardiac function and blood pressure

Renalase, a putative monoamine oxidase, has been recently identified by the group of G.V. Desir (1). It is considered to be a new renal hormone which is involved in the regulation of cardiac function and blood pressure by way of its assumed monoamino oxidase activity. The renalase protein contains a signal peptide for secretion (1-17 aa) overlapping a FAD binding region (3-42 aa) and an amino oxidase region (75-335 aa). The similarity to MAO A and B is only 13% and it is restricted to the first 80-100 aa. We have expressed the full-length human cDNA in Escherichia coli and purified the soluble protein. Here we report on its biochemical properties. We have demonstrated for the first time that indeed this renalase is a flavoprotein and shown that contains non-covalently bound FAD at variance with the MAO enzymes. Furthermore, our protein is devoid of catecholamine oxidase activity, thus casting doubts on the real substrate of this enzyme. 1. Xu J, Li G, Wang P, Velazquez H, Yao X, Li Y, Wu Y, Peixoto A, Crowley S, Desir GV., J Clin Invest (2005), 115(5):1275-80.