Toward an Understanding of Structural Insights of Xanthine and Aldehyde Oxidases: An Overview of their Inhibitors and Role in Various Diseases.

Almost all drug molecules become the substrates for oxidoreductase enzymes, get metabolized into more hydrophilic products and eliminated from the body. These metabolites sometime may be more potent, active, inactive, or toxic in nature compared to parent molecule. Xanthine oxidoreductase and aldehyde oxidase belong to molybdenum containing family and are well characterized for their structures and functions, in particular to their ability to oxidize/hydroxylate the xenobiotics. Their upregulated clinical levels causing oxidative stress are associated with pathways either directly involved in the progression of diseases, gout, or indirectly with the succession of other diseases such as diabetes, cancer, etc. Herein, we have put forth a comprehensive review on the xanthine and aldehyde oxidases pertaining to their structures, functions, pathophysiological role, and a comparative analysis of structural insights of xanthine and aldehyde oxidases' binding domains with endogenous ligands or inhibitors. Though both the enzymes are molybdenum containing and are likely to share some common pathways and interact with inhibitors in a similar manner but we have focused on structural prerequisites for inhibitor specificity to both the enzymes keeping in view of the existing X-ray structures. This review also provides futuristic implications in the design of inhibitors derived from inorganic complexes or small organic molecules considering the spatial features and structural insights of both the enzymes.