Trypsinlike Family of Enzymes

The trypsin-like family of enzymes requires cationic substrates for their enzymatic action. Common examples are tissue plasminogen factor, factor Xa, thrombin kallikrein and urokinase. These enzymes are known to bind to the side chains of lysine or arginine at a site (primary binding pocket) proximal to the reactive Ser195. The specificity is introduced mainly by the side chain of Asp189 present at the bottom of the primary binding pocket. Secondary interactions formed by amino acids binding adjacent to the primary pocket also confer specificity to individual members of the enzyme family.

Tissue kallikrein, that has kininogen as the natural substrate, shows a marked preference for arginine in the primary binding pocket and phenylalanine on the secondary site (Figure 1). The phenyl ring of phenylalanine is believed to form hydrophobic interactions with Trp215 and Tyr99. In contrast, trypsin demands less specificity from the secondary site residue. Thus, Burton and Lowe (1992) hypothesized that a structure based on the Phe-Arg dipeptidyl template should be designed and synthesized. The bio-mimetric ligand consisted of phenethylamine and p-aminobenamidine oriented on a triazine scaffold (Figure 2). Since the primary binding pocket of kallikrein lies in a depression, a hexamethylene spacer was introduced between the ligand and solid support to counteract any steric hindrance from the matrix backbone. On performing affinity chromatography with a crude pancreatic acetone powder, the designed synthetic ligand was able to purify kallikrein selectively with 110-fold purification factor. This efficiency compares well with the natural substrate ligands.

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

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