and seq id 3 and complements thereof the isolated or purified codon optimized dna consists of seq id 1 and or 3 and complements thereof variants of colg and colh exist wherein several amino acids differ for example one variant colg has 5 amino acid substitutions and one variant colh has 2 amino acid substitutions the codon optimized sequences of the invention can be modified so as to encode such variant collagenase proteins by utilizing substantially the same optimized codons as in seq ids 1 and 3 along with optimized codons encoding the amino acids which differ in those variants for example seq ids 1 and 3 may be used as the basis for encoding such variant colg and colh having five amino acid differences in colg from seq id 2 and two amino acid differences from seq id 4 as shown in tables a and b in one embodiment the dna for the variant colg is substantially identical to seq id 1 characterized by one or more of in another embodiment the dna for the variant colh is substantially identical to seq id 3 characterized by one or more of other variants may similarly be obtained using the teachings herein in one embodiment the sequences do not employ codons detrimental to e coli expression such as agg aga or cga encoding arg cta encoding leucine ata encoding isoleucine.