Does protein phosphorylation add a phosphate group, or does it add a phosphoryl group? Wikipedia seems to have conflicting info on it

Wikipedia on Phosphorylation, https://en.wikipedia.org/wiki/Phosphorylation says "In chemistry, phosphorylation of a molecule is the attachment of a phosphoryl group.....A phosphoryl group should not be confused with a phosphate group....The phosphoryl group plays the central role in phosphorylation...." And it mentions Protein Phosphorylation.

Wikipedia on Protein Phosphorylation , https://en.wikipedia.org/wiki/Protein_phosphorylation "Protein phosphorylation is a reversible post-translational modification of proteins in which an amino acid residue is phosphorylated by a protein kinase by the addition of a covalently bound phosphate group. "

Note- I am going to post an answer based on some really good info from Mithoron.


1 Answer 1


Note-Gotta credit Mithoron for this and if he posts an answer i'll accept his answer, as he deserves the rep for this answer.

There are two parts to this question

  1. Are there phosphate groups in ATP


  1. Is a phosphate group transferred.from the ATP , or is a phosphoryl group transferred from the ATP.

And also, you have to know the difference between a phosphate group and a phosphoryl group.

A phosphoryl group has three oxygens. A phosphate group has four oxygens.


enter image description here

Now you can look at ATP compared to ADP. There is no question that the difference is a phosphoryl group. Not a phosphate group.

enter image description here

I’ll use the general term phosphus compound to refer to something that may be a phosphate group and may be a phosphoryl group.

So when you look at ATP or ADP, do you draw lines to include four oxygens, or three oxygens. It’s arbitrary but that makes the difference to whether you would see phosphate groups, or phosphoryl groups.

But if you look at the first phosphor compound, and the O to the left of the P. That O is actually part of Adenosine.

Adenosine has that O, (though plus an H)

enter image description here

In answer to Are there phosphate groups in ATP.. One could maybe arguably(and not a good argument), consider there to be. if one draws the lines like that such that it considers the O from the adnosine to be part of the phosphate groups. Though(and to say phosphate groups would be a bad case, because), that O is from the adenosine. It’s Adenosine + three phosphoryl groups.

Phosphorylation involves the transfer of a phosphoryl group and not a phosphate group. And we know this because the thing that is transferred has three oxygens, not four oxygens.

Why then is it called triphosphate?

the naming "adenosine triphosphate" may have come from the fact that it can be formed by a condensation reaction between adenosine and a triphosphate group.

enter image description here

So ATP = adenosine + triphosphate - H - OH (i.e. minus water).

So, it might arguably be a bit of a misnomer, but well... it's stuck. (besides that perhaps apparently it should apparently be called adenosyl.... A follow up q I had was..Could you look at ATP as adenosine minus OH with triphosphate minus H. ? In which case, ATP could be seen legitimately as having the phosphate groups and that not being a misnomer. So the oxygen could legitimately be seen as part of the phosphor compounds.. Whether the oxygen came off the adenosine or off the triphosphate when they reacted, is perhaps arbitrary?

If you mean us counting the atoms on paper, then yeah, it is quite arbitrary whether we take the OH away from adenosine or the triphosphate. But in the biosynthesis of ATP, (without checking one could bet,), the oxygen comes from adenosine, i.e. it's (adenosine - H) + (triphosphate - OH).


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.