Lipase specificity - (May/11/2009 )

Dear all,

We know that lipase, like all enzymes, is specific but I read that it doesn't hydrolyze all three ester linkages in a triglyceride. Is it true? Can you guys who are working with lipase confirm this?

I'm growing my bacteria on oil and after a few days, I get a white cloudy medium (it was clear) and I believe that it's emulsified. Having said that, I think a mono- or a diglyceride may contribute to that.

Please advise. Thank you!

You are right, lipase generates mono-glycerols. It only acts on the ester bonds at carbon 1 and 3 (the alpha positions) so the products are 2 moles of fatty acids and one mole of 2-acylglycerol (a beta-monoglycerol).

Steric hindrance is presumambly to blame for the inability of lipase to act on the beta carbon but there is some degree of spontaneous isomerisation to the alpha form. The results in a much slower production of gycerol and yet more fatty acid. In clinical lipase assays the glycerol has to be taken into account.

The lipase action is dependent upon bile acids and a cofactor (co-lipase). The bile acids prevent other proteins from binding to the substrate surface. Lipase itself acts only on the interphase betwen water and the substrate (i.e. when the substrate is in the emulsified form).

NaCl (c100mmol/L) should activate your lipase if need be.


Hope that helps.

Dreamchaser,

Your interesting question was the topic of hot debate and intrigue in my lab. One of our lipid specialists pointed out that in some thermophilic and halophilic bacteria, the lipid structure is not ester-bonded but ether-bonded. This is a stronger bond than the ester link. I think also the bacterial syetem involves a sodium gradient as well as a proton-motive force whereas the mamalian system only involves the protoin-motive force. I'm not sure how the sodium ions contribute to the system. I don't know if mamalian lipase would act on these ether links. What source are you using?

Is this relevant to your bacteria?