Structural and functional investigation of astaxanthin binding to the catalytic domain of matrix metalloprotease MMP-13

Matrix metalloproteases (MMPs) are zinc-containing proteases involved in the remodeling and breakdown of extracellular matrix proteins. Overexpression of the MMPs has been associated with a variety of diseases ranging from periodontal disease and arthritis to tumor invasion and metastasis. The majority of the more powerful synthetic inhibitors of MMPs incorporate a hydroxamate group, but exhibit low selectivity and are toxic. In a recent modeling study, Astaxanthin (AST), a carotenoid with potent antioxidant property, has been shown to be a potential inhibitor of MMP-13 function by occupying a binding site near the active center of the enzyme (Bika´di et. al. 2006). In our ongoing project, we investigate the binding of AST to the catalytic domain of MMPs using biochemical and ultimately crystallization to validate the proposed action of AST. Along these lines, the catalytic domain of MMP-13 (cdMMP-13) was expressed in E.coli BL21(DE3) CodonPlus and refolded using a novel effective refolding method. Our results reveal that AST has a potent inhibitory effect on cdMMP-13 activity, however, determination of IC50% or Ki is difficult due to fast oxidation and structural instability of AST. Ongoing work aims at optimizing the inhibition conditions and improving the refolding yield to allow analyzing structure and function of the AST-bound MMP-13 in more detail.
Bikádi et al. (2006) Bioorg Med Chem 14:5451-8.