I have successfully used chloroperoxidase to oxidize the primary alcohol of an N-terminal serine to an aldehyde. I recently tried this on a different peptide that had a C-terminal serine ( R-Ser-OH) or (the information I was given was unclear) a C-terminal serine-amide (R-Ser-NH2). Multiple reactions have failed to oxidize this peptide. My question is two-part: (1) does chloroperoxidase oxidize serine alcohol to aldehyde as well on the C-terminal as on the N-terminal? and (2) if the serine is actually a serine-amide, will that stop the chloroperoxidase from oxidizing the alcohol?
You're right, Ron, it is the Caldariomyces heme chloroperoxidase. I hope someone will have an answer.
I have worked with myeloperoxidase but not chloroperoxidase. In that case the aldehyde is formed from the amino group of the serine, not the hydroxyl. The HOCl generated by the enzyme generates an intermediate chloramine which breaks down to the aldehyde. See Anderson et al, J Clin Invest 99, 424,1997.
Christine Winterbourn
Thanks, Christine. I'll check out the reference as soon as I get home tonight.
Ron, no, there is no chloride present. It is the peptide, chloroperoxidase, and hydrogen peroxide in sodium acetate buffer at pH 5.0. Thanks for the reference, though. This works well with a peptide containing N-terminal serine, but fails with our peptide where the serine is on the C-terminus.
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