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We're an undergraduate independent research team and we are having trouble purchasing commercial proline iminopeptidase as it is unavailable on Sigma Aldrich and very expensive on other websites. We need to test that this peptidase will cut a series of tripeptides we are synthesizing in e coli.

Could we purchase proline aminopeptidase instead of proline iminopeptidase; will the peptidase function the same way?

This paper says that they are the same, but this paper says that they are different. Does anyone have any experience with this commercial peptidase?

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    $\begingroup$ Chemically, proline does not contain an imino group. goldbook.iupac.org/I02959.html More on topic, you can send an email to the manufacturer of the aminopeptidase and ask if it cuts the tripeptides. $\endgroup$ – March Ho Jun 1 '15 at 19:44
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    $\begingroup$ The peptidase cuts the tripeptides after the proline in that sequence. The purpose of purchasing this peptidase is to compare our experimental results (the results of the cleavage) to the results of the commercial peptidase cleavage. We work in synthetic biology so both the tripeptides and the peptidase will be in a single plasmid. $\endgroup$ – Kathryn Jun 1 '15 at 20:03
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There are two related enzymes that cleave an N-terminal residue. Enzyme 3.4.11.9 cleaves any residue from a peptide when the next residue is proline. Enzyme 3.4.11.5 cleaves an N-terminal proline from a peptide. Unfortunately, it appears that both are sometimes referred to as proline aminopeptidase. However, only 3.4.11.5 is referred to as proline iminopeptidase.

The vendor should certainly specify which enzyme they are offering.

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