Molecular docking of Subtilisin K2, a fibrin-degrading enzyme from Indonesian moromi, with its substrates

Abstract

Fibrinogen supplies the primary building block of the blood clot or thrombus after α-thrombin converts fibrinogen to fibrin during the final phases of coagulation. When the homeostasis system is disrupted, blood clots that aggregate in the blood vessels can lead to thrombosis. Fibrin-degrading enzyme from Bacillus subtilis K2 (Subtilisin K2) of Indonesian moromi has many excellent characteristics apart from its strong fibrinolytic activity. Bioinformatic analysis using the CDART webserver indicated that the enzyme appeared to share a conserved domain with the peptidase s8 superfamily also known as the subtilase family. This study used molecular docking between these fibrin-degrading enzymes and specific substrates (fibrin and fibrinogen) using the HADDOCK webserver and aimed to predict the enzyme mechanism of action. This analysis revealed that the enzyme interlocked with the two substrates; however, it suggested no productive interactions between Subtilisin K2 and fibrinogen. A hydrolysis reaction is suggested between Subtilisin K2 and the fibrin substrate. There was a strong indication that amino acids Asp19, His51, and Ser208 in Subtilisin K2’s active site interacts with Leu168, Ile171, and Leu172 of the fibrin substrate with a ∆G of -19.4 kcal/mol. Subtilisin K2 tends to act more as a fibrin-degrading enzyme than as a fibrinogen-degrading enzyme.

Keywords:
binding affinity; domain; fibrinogen; fibrin; molecular docking