Relationship between the individual collagenases of Clostridium histolyticum: evidence for evolution by gene duplication

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Abstract
The relationship between 6 collagenases (.alpha., .beta., .gamma., .delta., .epsilon. and .zeta.) was investigated. Chemical modification reactions established that all 6 enzymes contain essential carboxyl, tyrosine and lysine residues. Circular dichroism spectra of the peptide bond region show that the secondary structures of the collagenases are very similar. Ouchterlony double-immunodiffusion experiments carried out with antiserum prepared against .beta.-collagenase indicate that all 6 collagenases are cross-reactive. Reverse-phase high-pressure liquid chromatography elution profiles of tryptic digests of these collagenases and sodium dodecyl sulfate electrophoressis gels of the peptides formed on reaction with CnBr were obtained. Apparently, class I collagenases have extensive sequence homology with each other and the class II collagenases have extensive sequence homology with each other, but the enyzmes in the 2 classes have substantially different sequences. .beta.-Collagenase probably consists of domains than have homologous amino acid sequences, which may have arisen by full or partial intragenic gene duplication. This may account for the unusually high MW of this and the other collagenases. On the basis of the similarities between the collagenases in the 2 classes, 1 class apparently evolved from the other by gene duplication followed by independent evolution by point mutations to yield enzymes with different substrate specificities.