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I am currently examining the acyl transfer catalysis activity of several enzymes that I was told are all lipases. Through reading a couple of papers including these enzymes I found out that all of them are hydrolases with promiscuous acyltransfer activity. Specifically one of the enzymes is a carboxyl-esterase, one is an aryl-esterase and the third one is an acyl-esterase. I know that esterases are part of hydrolases and lipases are basically fat-splitting esterases. Lipases also catalyze transesterification = acyl transfer, just like all of the enzymes I am working with do. I just don't understand the classification of all these enzymes as lipases. Can someone explain the connection to me?

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    $\begingroup$ Could you clarify. You explain that you understand that the enzymes in question are all "fat-splitting" i.e. lipid-hydrolysing esterases. More specifically they hydrolyse lipids that belong to the class ester (e.g. triglycerides) rather than lipids in general such as free fatty acids or cholesterol. Such enzymes are given the trivial generic name lipase. (They have more specific systematic names.) What is it that you do not understand? Do you want examples of systematic names or what? $\endgroup$
    – David
    Mar 6 at 11:44
  • $\begingroup$ The assay we are working with is using para-nitrophenyl butyrate as a substrate. This substrate is usually used for investigating esterase, as well as lipase activity. I read that "Lipases can be distinguished from carboxyl esterases by their substrate spectra, using p-nitrophenyl palmitate (cleaved by lipases) versus p-nitrophenyl butyrate (cleaved by esterases)" (Source: scielo.br/pdf/cta/v31n3/a09v31n3.pdf). So shouldn't the enzymes I am using be classified as esterases, rather than lipases? $\endgroup$
    – Alina
    Mar 8 at 16:15
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    $\begingroup$ I think your problem is one of the use of trivial names (such as lipase) and systematic EC names, which I have answered here Origin of enzyme names. $\endgroup$
    – David
    Mar 9 at 12:29
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    $\begingroup$ This is further to my previous comment which was autogenerated when I voted to close your question as already having an answer. I would stress that "lipase" is not a systematic name but a trivial name, that the names people use for enzymes (as of other things) depends on what they were taught and what interests them. If you are interested in lipids, the name lipase appeals, if you are a chemist, not. See also my answers for other enzymes here and here. $\endgroup$
    – David
    Mar 9 at 12:38