T4-lymphocyte endoprotease responsible for the proteolytic processing of HIV-1 gp160, like Kex2p endoprotease, is a calcium-dependent enzyme.

In the present study we show that precursor gp160 is cleaved in the HIV-1 infected CEM (CD4+) cell line preferentially in the presence of calcium ions demonstrating that the responsible cellular endoprotease is a calcium-dependent enzyme. Taking into account this similarity, a synthetic peptide modelling the cleavage site of HIV-1 envelope glycoprotein precursor was used as substrate for Kex2p. Results obtained clearly showed that the processing enzyme Kex2p (EC 3.4.21.61), a subtilisin-like serine protease that is encoded by the KEX2 gene of yeast Saccharomyces cerevisiae is able to cleave correctly this peptide at the potential cleavage site.