Further inhibition studies on guanidinobenzoatase, a trypsin-like enzyme associated with tumour cells

Identification and molecular cloning of a novel amphibian Bowman Birk-type trypsin inhibitor from the skin of the Hejiang Odorous Frog; Odorrana hejiangensis

In this study, an amphibian (Odorrana hejiangensis) skin extract was fractionated by reverse phase HPLC and fractions were screened for trypsin inhibitory activity. Using this initial approach, a novel trypsin inhibitory peptide was detected with an apparent protonated molecular mass of 1804.83 Da, as determined by MALDI-TOF mass spectrometry. It was named Hejiang trypsin inhibitor (HJTI) in accordance. The primary structure of the biosynthetic precursor of HJTI was deduced from a cDNA sequence cloned from a skin-derived cDNA library. The primary structure of the encoded predicted mature active peptide was established as: GAPKGCWTKSYPPQPCS (non-protonated monoisotopic molecular mass--1802.81Da). On the basis of this unequivocal amino acid sequence, a synthetic replicate was synthesized by solid phase Fmoc chemistry. This replicate displayed a moderately potent trypsin inhibition with a K(i) of 388 nM. Bioinformatic analysis of the primary structure of this peptide indicated that it was a member of the Bowman-Birk family of protease inhibitors. The substitutions of Gln-14 and Ser-17 by Lys, resulted in an increase in cationicity and a small increase in potency to a K(i) value of 218nM. Neither HJTI nor its synthetic analog, possessed any significant antimicrobial activity.

Mechanisms of C6 glioma cell and fetal astrocyte migration into hydrated collagen I gels

Fetal basal ganglia astrocytes and C6 glioma cells were plated on the surface of 1.5 cm thick hydrated collagen I wafers. Both cell types migrated through the entire thickness of the wafer within 1 day after plating. The collagen in the wafer was digested and the fine collagen I fibrils were clumped into large strands. By 2-3 days, the collagen strands were digested from the wafers and replaced by a mass of fetal astrocytes or C6 cells joined by their processes. The collagen I digestion and cell migration suggested protease production. In a second series of experiments, cultured C6 cells and E14 fetal astrocytes were immunohistochemically stained for the presence of plasminogen activators as an index of protease production. Both tissue (tPA) and urokinase (uPA) types were observed. Fetal astrocytes and C6 cells were also positive for guanidinobenzoatase, a serine protease associated with migrating cells. These data demonstrate that rapid migration of the cells on and through collagen I fibrils is concomitant with expression of plasminogen activators and proteases which can either activate or function as collagenases and release the cells from the substrate.

Inhibition of guanidinobenzoatase by a substrate for trypsin-like enzymes

Guanidinobenzoatase is a proteolytic enzyme capable of degrading fibronectin and is a tumour associated enzyme. Guanidinobenzoatase has been shown to be an arginine selective protease and is distinct from trypsin, plasmin and thrombin, the latter enzymes can be assayed with bis(carbobenzyloxycarbonyl-L-argininamido)-Rhodamine or BZAR. Guanidinobenzoatase is inhibited by BZAR when the enzyme is assayed in free solution and when the enzyme is cell-bound in frozen sections of tumour containing tissues. It is proposed that BZAR and its analogues may be of value in inhibiting tumour cell invasion in vivo and also that the selectivity of BZAR may be used to direct cytotoxic drugs to tumour cells possessing active guanidinobenzoatase.