Human bleomycin hydrolase: molecular cloning, sequencing, functional expression, and enzymatic characterization

The open reading frame encoding human bleomycin hydrolase (hBH) consists of 1365 bases and produces a protein with 455 amino acids. The protein is 40% and 89.5% identical to the yeast and rabbit bleomycin hydrolase, respectively. The protein functions as a protease and efficiently degrades bleomycin A2 and B2. Most human organs have low levels of hBH while tumor cell lines have high hBH levels. The high hBH levels are probably responsible for the resistance of tumor cells to bleomycin. The gene produces a 52 kDa protein in Spodoptera frugiperda Sf6 cells that behaves as an aminopeptidase.