Lysosomes

taguebw at REMOVEwfu.edu taguebw at REMOVEwfu.edu
Wed Oct 22 17:25:13 EST 1997


In article <344e617a.473734 at news.demon.co.uk>, andy at biology.demon.co.uk wrote:

> On Thu, 16 Oct 1997 21:55:23 -0400, "Jeff" <knight at ionsys.com> wrote:
> 
> >In biology class we were discussing lysosomes, and how they can carry
> >digestive enzymes to food vacuoles, and digest anything inside the cell.  I
> >asked the teacher what it is about the membrane surrounding the lysosome
> >that prevents the enzymes from digesting it.  She was unsure of this and I
> >am very curious.  If anyone could help out with an explanation that would be
> >great!  Thanx!
> >
> >- Jeff
> >- knight at ionsys.com
> >
> >
> Lysosomes are an example of membrane boune organelles. they are
> enclosed in a lipid unit membrane.  the enzymes within a lysosome are
> proteolitic that is they digest protein - peptide bonds. therfore they
> are unable to digest the lipid membrane that encloses them.

This is not correct. Lysosomes contain many different kinds of acid
hydrolases: nucleases, glycosidases, lipases, phosphatases,
phospholipases, etc. in addition to proteases. Lysosomes can degrade
complete organelles such as mitochondria -- including membrane components
-- using these hydrolases.

This does not of course answer the orignal question of why lysosomes do
not self-digest. I don't know the answer to that one, but would guess that
the membrane proteins and lipids exposed to the lumen of the lysosome are
constructed to be more resistant to the various hydrolases. Hope someone
else can offer a more complete answer to this interesting question.

My 2 electrons,
Brian

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