It has been found that Ser His could cleave bovine serum albumin(BSA), with the most suitable pH around 6.0. The kinds of buffers have different influences on the cleavage activity. The phosphate buffer and BR buffer are the most effective. The hydroxyl group of the serine residue is the essential functional group for the cleavage, while the amide bond, imidazole, and carboxyl group of Ser His increase the cleavage activity.
The effects of the amino, hydroxyl, imidazole and carboxyl groups of Ser His on DNA cleavage reaction were studied. It was found that the amino and hydroxyl groups were essential for the DNA cleavage activity of Ser His, and that anyone of them blocked would result into the loss of cleavage activity. The carboxyl group was not the necessary group. The presence of the imidazole group would enhance the cleavage activity. However, the histidyl serine dipeptide, as the formula isomer of Ser His with the inverse peptide sequence, could not cleave DNA at all. Based on the above experimental results, a presumed cleavage mechanism of Ser His on DNA was proposed. [WT5HZ]
