An isopeptide bond splitting enzyme from Hirudo medicinalis similar to gamma-glutamyl transpeptidase.

A new enzyme from Hirudo medicinalis capable of splitting gamma-glutamyl-p-nitroanilide and Glu--Lys-(N6-gamma-glutamyllysine) (isopeptidic bond between the epsilon-amino group of lysine and the gammacarboxylic group of glutamic acid) isopeptide bonds was purified. The protein was partially sequenced at the amino acid level, and the complete nucleotide and amino acid sequences were determined after cDNA cloning. The new enzyme has more than 60% similarity at the amino acid level to vertebrate gammaglutamyl transpeptidase (gamma-GT). According to the cDNA, the new protein has a molecular mass of 65 521 Da and a length of 600 amino acids.