Some of the pioneering work on this was done by Katchalsky,
Katchalsky-Katzir and collaborators in the 70s, a major conclusion
being that Km(app) or S0.5(app) can be significantly raised over the
'solution' values when the enzyme is bound to a membrane. The effect
is somewhat similar to the concentration polarisation
recognised/described in the fields of electrochemistry and membrane
filtration - as Clause says the Chem Eng literature is where a lot
of this stuiff is found. Also look out in 70s and early 80s for
papers on this by D. Thomas and colleagues at Univ. Compiegne.
Best wishes,
Douglas.
> Petr, the alternative, more rigorous approach to membrane-bound
> enzyme kinetics originate basically from the Chemical Engineering
> field; it differentiates between intrinsic (microscopic, as in
> solution) and inherent (solely resulting from their physical state)
> properties of immobilized enzymes. The combination of both yields
> the effective properties of the catalytic system (macroscopic, as
> observed out of the black box).
>> The latter, most often dealt-with by most biologists, yield a
> distorted picture of the system's behavior, especially when the
> interpretation of the results is based on a (tacite) assumption that
> "ideal" conditions prevail...
>> If you're interested please refer to this central (relatively
> recent) review:
> *Engasser, J.-M. and C. Horvath (1976). Appl. Biochem. Bioeng. 1:127-220.
>> A fascinating discussion, pertaining to the effective consequences
> of enzyme organization can also be found at:
> *Ricard, J., N. Kellershohn, et al. (1989). Spatial order as a source of
> kinetic cooperativity in organized bound enzyme systems. Biophys J
> 56:477-487.
>> The modelling of these aspects is tough and refractive to automation
> due to the non-linearity of the underlying phenomenological
> differential equations. I'd love to see packages like 'gepasi',
> 'biokin', 'jarnac' etc. (sorry I can't enumerate all...),
> implementing that.
>> Some of my (and many cited others') work using localized probes
> deals with the "diagnosis", demonstration and discussion of
> heterogeneous effects in cellular catalysis:
>> *Aflalo, C. and N. Shavit (1984). A new approach to the mechanism of
> photophosphorylation: modulation of ATP synthetase activity by
> limited diffusibility of nucleotides near the enzyme. Curr. Top.
> Cell. Regul. 24: 435-445.
>> *Aflalo, C. and M. DeLuca (1987). Continuous monitoring of ATP in the
> microenvironment of immobilized enzymes by firefly luciferase.
> Biochemistry 26:3913-3919.
>> *Aflalo, C. (1991). Biologically localized firefly luciferase: a tool to
> study cellular processes. Int. Rev. Cytol. 130:269-323.
>> *Aflalo, C. and L. A. Segel (1992). Local probes and heterogeneous
> catalysis: a case study of a mitochondria-luciferase-hexokinase
> coupled system. J. Theor. Biol. 158:67-108.
>> *Aflalo, C. (1997). Localized firefly luciferase probes ATP at the surface
> of mitochondria. J. Bioenerg. Biomembr. 29:549-559.
>> Sincerely,
>> Claude
>> Claude Aflalo ########################## Phones: Office
> 972-7-6472118 #### Unit for Science Teaching/Dept. of Life Sciences
> Lab 972-7-6472119 Ben Gurion University of the Negev
> Fax 972-7-6472890 P.O.Box 653 email:
>aflaloc at bgumail.bgu.ac.il Beer Sheva 84105 Israel ### URL:
>http://www.bgu.ac.il/~aflaloc/aflalo.html>>>> ---
>>>(Prof.) Douglas B. Kell, Cledwyn Building,
Institute of Biological Sciences, University of Wales,
Aberystwyth SY23 3DD
Tel: +44 1970 622334 Fax: +44 1970 622354
dbk at aber.ac.ukhttp://gepasi.dbs.aber.ac.uk/home.htm
---
