Why are concentrated enzymes more stable?

Dima Klenchin klenchin at macc.wisc.edu
Sat Jun 22 12:46:19 EST 1996


In article <1996Jun21.192809.21463 at alw.nih.gov>,
   bernard at elsie.nci.nih.gov (Bernard Murray) wrote:
->In article <aquilla.1185604211N at emba-news.emba.uvm.edu>, 
->aquilla at salus.med.uvm.edu says...
->>
->>Anyone care to guess or have a reference?
->>Tracy
->
->Enzymes in concentrated
->solutions are not more stable per se but the chance of them being
->inactivated depends on the volume (and/or surface area) rather than
->the concentration of the solution.

Many proteins ARE more stable in concentrated form than in diluted,
and this cannot be explained by absorption and/or oxidation on the 
surface. 

Everyone can do the simple experiment that I did ~ 10 years ago
when I was first puzzled by this phenomenon (just for fun). IgG-AP 
conjugate was tested in ELISA after storage for 2 mo at +4C  in the 
following conditions:

	30 ug/ml + 0.5 mg/ml BSA
	30       - BSA
	1  ug/ml + BSA
	1  ug/ml - BSA

ALL tubes were preadsorbed with BSA, and protease inhibitors 
cocktail (many but I don'r remember which exactly) was added
and ALL tubes were flushed with argon. 

Activity of 1 ug/ml - BSA sample was at least an order of magnitude
less than everything else. No measurable binding to the tube walls
was detected. 

I cannot claim anything for sure for I was an undergrad at that
time, but I do believe that this result can be reproduced.

Just read a reply of Klaus Salger <salger at zi.biologie.uni-muenchen.de>.
His explanation is very probable. The key here is whether indeed

>if the oxygen concentration is rate limiting?

- Dima




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