Azaphenylalanine-based serine protease inhibitors induce caspase-mediated apoptosis

Potential Anticoagulant Activity of Trypsin Inhibitor Purified from an Isolated Marine Bacterium Oceanimonas Sp. BPMS22 and its Kinetics

Protease inhibitors control major biological protease activities to maintain physiological homeostasis. Marine bacteria isolated from oligotrophic conditions could be taxonomically distinct, metabolically unique, and offers a wide variety of biochemicals. In the present investigation, marine sediments were screened for the potential bacteria that can produce trypsin inhibitors. A moderate halotolerant novel marine bacterial strain of Oceanimonas sp. BPMS22 was isolated, identified, and characterized. The effect of various process parameters like salt concentration, temperature, and pH was studied on the growth of the bacteria and production of trypsin inhibitor. Further, the trypsin inhibitor was purified to near homogeneity using anion exchange, size exclusion, and affinity chromatography. The purified trypsin inhibitor was found to competitively inhibit trypsin activity with an inhibition coefficient, K_i, of 3.44 ± 0.13 μM and second-order association rate constant, k_ass, of 1.08 × 10³ M^-1 S^-1. The proteinaceous trypsin inhibitor had a molecular weight of approximately 30 kDa. The purified trypsin inhibitor showed anticoagulant activity on the human blood samples.

Selective cytotoxicity of amidinopiperidine based compounds towards Burkitt's lymphoma cells involves proteasome inhibition

Serine proteases have proven to be promising pharmacological targets in contemporary drug discovery for cancer treatment. Since azaphenylalanine-based compounds manifest cytotoxic activity, we have selected serine protease inhibitors designed and synthesized in-house with large hydrophobic naphthalene moiety for screening. The cytotoxic potential of screened molecules was correlated to modifications of R¹ residues. The most cytotoxic were compounds with greater basicity; amidinopiperidines, piperidines and benzamidines. Amidinopiperidine-based compounds exert cytotoxicity in low µM range, with IC₅₀ 18 µM and 22 µM for inhibitors 15 and 16 respectively. These compounds exhibited selective cytotoxicity towards the Burkitt’s lymphoma cells Ramos and Daudi, and proved nontoxic to PMBC, Jurkat and U937. They induce caspase-dependent apoptotic cell death, as demonstrated by the use of a pan-caspase inihibitor, zVADfmk, which was able to rescue Ramos cells from compound(s)-induced apoptosis. We confirm a disruption of the pro-survival pathway in Burkitt’s lymphoma through NFκB inhibition. The accumulation of phosphorylated precursor (p105) and inhibitory (IκB) molecules with no subsequent release of active NFκB implicated the involvement of proteasome. Indeed, we show that the amidinopiperidine-based compounds inhibit all three proteolytical activities of the human 20S proteasome, with the most prominent effect being on the trypsin-like activity. Consistently, treatment of Ramos cells with these compounds led to an increase in ubiquitinated proteins. The amidinopiperidine-based serine protease inhibitors presented are, as selective inducers of apoptosis in Burkitt’s lymphoma cells, promising leads for the development of novel chemotherapeutics.