Puff adder venom contains a protease capable of cleaving the gamma-chain of cross-linked D-dimer, derived from the plasmin digestion of fibrin, into apparently symmetrical monomers. The cross-linked gamma-chains are separated in the process without apparent loss of mass and without loss of the substituent at the glutamine cross-link site, if fluorescent D-dimer (the lysine analogue dansylcadaverine used as substituent) is used as substrate [Purves, L. R., Purves, M., Lindsey, G. G., & Linton, N. J. (1986) S. Afr. J. Sci. 82, 30]. The gamma-chain from puff adder venom digested D-monomer was isolated and cleaved by cyanogen bromide, and the carboxy-terminal peptide was isolated and sequenced. The carboxy-terminal peptide composition indicated a lower content of histidine, leucine, and glycine than expected. Manual microsequencing by gas-phase Edman degradation demonstrated that two amino-terminal ends were present. By use of the known sequence of the human fibrinogen gamma-chain, the sequencing data could be resolved into a dipeptide cross-linked between lysine-406 and either glutamine-398 or -399 (residues 6 and 13 or 14 from the carboxy-terminal end of the gamma-chain) with the loss of residues 401-404 that occur between the cross-link sites of both antiparallel cross-linked gamma-chains. D-dimer is therefore separated into monomers by cleavage of the gamma-chain between the cross-link sites. Two symmetrical fragments are produced consisting of a cross-linked dipeptide with the loss of four amino acids.(ABSTRACT TRUNCATED AT 250 WORDS)

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