Amino acid hydrolysis via 6M HCl cleaves all the amide/peptide...

Question

Amino acid hydrolysis via 6M HCl cleaves all the amide/peptide bonds of a protein. What do you suppose happens to the amide bonds in the R-groups of Asn & Gln residues upon treatment with 6M HCl?

Accepted Answer

So this practice problem says, amino acid hydrolysis via 6 molar hydrochloric acid cleaves all of the amide slash peptide bonds of a protein? And then it asks, what do you suppose happens to the amide bonds in the R groups of both asparagine and glutamine residues upon treatment with 6 molar hydrochloric acid. And so down below, I've drawn the structure of the asparagine amino acid on the left as well as the glutamine amino acid on the right. And what you'll notice is that in the R groups of both spargine and glutamine, that there is indeed an amide bond that is present and is highlighted in green here. And we know that upon exposure to 6 molar hydrochloric acid, that all of the amide and peptide bonds of a protein are going to be cleaved. And that includes the amide bonds that are found in the R groups of both asparagine and Glutamine. And so starting with asparagine on the left, we know that upon exposure to 6 molar hydrochloric acid, that the amide bond in the R group of the spargine is going to be cleaved. And that is gonna result in the same exact r group, except instead of having the amino group at the end, there's going to be an oxygen amino acid. And amino acid. And so aspartic acid's three letter code is ASP, and its one letter code is just d. And so what we're saying here is that upon exposure to 6 molar hydrochloric acid, that a spare gene residues can be converted into aspartic acid residues. Now if we apply that same logic over here on the right to glutamine, we know that upon exposure to 6 molar hydrochloric acid, that the amide bond in glutamine's R group is going to be cleaved. And that is going to result in the same exact R group, except instead of having this amino group at the end, there's going to be an oxygen atom at the end and a carboxylate group at the end of the r group. And so this r group right here is really the r group of a glutamic acid, amino acid. And glutamic acid's, three letter code is glu, and its one letter code is just an e. And so, again, what we're saying here is that upon 6 molar hydrochloric acid exposure, that Glutamine residues can be converted into Glutamic acid residues. And really what this practice problem is hinting at is that even though we know amino acid hydrolysis can be used to determine the amino acid composition of a protein, it does not always allow for complete amino acid analysis. And part of the reason has to do with the fact that asparagine residues can be converted to aspartic acid residues, and glutamine residues can be converted to glutamic acid residues. And so, that is part of the reason why we also have several different, protein cleavage techniques to be able to determine the amino acid composition and the amino acid, sequence of our protein. Such as, for instance, peptidases, which again, we'll talk a lot more about peptidases later in our course. But for now, this concludes our practice problem, and I'll see you guys in our next video.

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Amino acid hydrolysis via 6M HCl cleaves all the amide/peptide bonds of a protein. What do you suppose happens to the amide bonds in the R-groups of Asn & Gln residues upon treatment with 6M HCl?

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