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Does anyone know if the human gastic lipase has a quaternary structure? If not, why not? I can not seem to find this information anywhere.

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  • $\begingroup$ I'm voting to close this question as off-topic because it might be better asked in a biochemistry group. $\endgroup$ Jan 7 '20 at 12:00
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    $\begingroup$ I think the question should be reopened because the OP addressed a real gap in the available information on this protein. I have since edited the images on Wikipedia and Proteopedia - we will see if these edits stick. $\endgroup$ Jan 8 '20 at 13:33
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There is a crystal structure of human gastric lipase (PDB ID 1hlg). The accompanying paper does not mention any quaternary structure and shows the protein as single chain. Automated analysis of the coordinates support that. The enzyme is glycosylated, so the molar mass does not match the one expected from the sequence. The apparent molar mass determined experimentally is about 50,000 g/mol, corresponding to a monomer.

However, the annotation in the structure (probably erroneously) say that the biological assembly consists of the two chains in the asymmetric unit. Also, there is a report that the size of the molecule changes with pH (90,000 g/mol at pH 6 vs 45000 g/mol at pH 3).

The same group that solved the human lipase structure later solved the dog lipase structure (in an open conformation with a bound ligand) where the annotation in the PDB deposition says it is a monomer. I doubt that there are interspecies differences between dog and human in terms of quaternary structure, so that would be another piece of evidence supporting that the human enzyme is a monomer in its native form.

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  • $\begingroup$ @Leigh Keep in mind you can also accept answers that were useful to you. $\endgroup$
    – andselisk
    Jan 7 '20 at 11:52

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