부산대학교 도서관

Three isoforms of extracellular Arg-specific proteases of P. gingivalis, W50, HRgpA, RgpAcat and mt-RgpAcat, which are all products of the same gene, show identical enzymatic properties toward small chromogenic substrates but have different subunit organisation and molecular size. In order to examine the potential inhibition of these proteases in vivo by host protease inhibitors, the interaction of HRgpA (~ 110 kDa) and RgpAcat (~ 55 kDa) with human α2M and their cytotoxicity toward cultured fibroblasts were investigated. Both enzymes formed complexes with α2M as shown by gel filtration chromatography and both cleaved the ‘bait’ region at Arg696-Leu697. However, whereas (α2M-RgpAcat) complex was unable to hydrolyse large substrates such as hide powder azure, (α2M-HRgpA) complex hydrolysed both small and large substrates. HRgpA was able to bind to α2M saturated with trypsin and also to methylamine-treated α2M. This suggested that HRgpA is able to bind to both ‘slow’ and ‘fast’ forms of α2M and formation of (α2M:HRgpA) complex does not trap HRgpA and cause inhibition of activity toward hide powder azure. However, the (α2M-HRgpA) complex is not able to cleave other α2M molecules, which suggests that the active site of HRgpA in the complex is constrained probably due to steric reasons. The (α2M-HRgpA) complex was cytotoxic to 3T3 cells, causing them to round up and detach from the surface with a reduction in metabolic activity.