It also contains an aspartate and histidine in the triade which are bothdependent on pH and salt. The stability of the oxy-anion is potentially the most important step in hydrolysis transitiion state.

http://www.enzim.hu/data/pdf/16003488.pdf

Serine and threonine phosphatases belonging to the family of PP2C can be sensitive and activated by Mn, MG and Ca 10 mM ionic concentration.

Best wishes, Borbala Gesser

Activity of Serine protease is not only depend upon ionic strength but so many other factor like pH, temperature and inhibitors are also influence the protease activity.

Here i attached one article link. i hope it will helpful for you.

http://jb.asm.org/content/121/3/933.full.pdf

Hi. In general it is true that serine proteinase activities against small synthetic substrates decrease with increasing salt concentration. There has been a lot of work done in this field and you might want to narrow the search to your proteinase.

http://scholar.google.com/scholar?as_vis=1&q=%22serine+protease%22+%22ionic+strength%22+%22active+site%22+salt&hl=en&as_sdt=1,21

It also contains an aspartate and histidine in the triade which are bothdependent on pH and salt. The stability of the oxy-anion is potentially the most important step in hydrolysis transitiion state.

http://www.enzim.hu/data/pdf/16003488.pdf

Purification, kinetic characterization and properties of a novel thermo-tolerant extracellular protease from Kluyveromyces marxianus IFO 0288 with potential biotechnological interest.

( depends on the enzyme)

As many of the others have alluded to, the answer will depend on the rate-limiting step of the specific protease and substrate you are looking at. Here is a review that describes the mechanism and the kinetic rate constants: Serine Protease Mechanism and Specificity, Lizbeth Hedstrom, Chemical Reviews 2002 102 (12), 4501-4524. http://dx.doi.org/10.1021/cr000033x

Serine potease activity depends on many factors as already mentioned such as pH temperature , substrate, ions, ...

*Two detergent stable alkaline serine-proteases from Bacillus mojavensis A21: Purification, characterization and potential application as a laundry detergent additive. Anissa Haddar, Rym Agrebi, Ali Bougatef, Noomen Hmidet, Alya Sellami-Kamoun, Moncef Nasri (2009). Bioresource Technology 100, Issue 13 : 3366-3373

**

Biochemical and molecular characterization of a detergent stable alkaline serine-protease from a newly isolated Bacillus licheniformis NH1. Nedra El Hadj-Ali, Rym Agrebi, Basma Ghorbel-Frikha, Alya Sellami-Kamoun, Safia Kanoun and Moncef Nasri (2007) . Enzyme and Microbial Technology, 40, Issue 4: 515-523

Ok, thanks a lot.

Cheers!

I would also be aware of the ionic effects in the range of interest. The most critical zones are likely to be at very low I (say 5-25mM) and very high values - - the effects at these two extrema are important.

Second, if you are conducting experiments, remember that the ionic strength of a buffer will change the pKa of the buffer species, and unless you compensate for this, the pH may shift - yielding an 'apparent' I effect.

To calculate thermodynamically correct buffers (for typical biological experiments) have a look at this calculator:

www.liv.ac.uk/buffers

(I'm aiming for a million litres before I retire!)

the effect of ionic strength also depends on the source of the enzyme. Halotolerant proteases, halophilic proteases and acidophilic proteases all these are very sensitive to the ionic strength of the medium. The effects are more in these class of proteases than from the other sources. Ofcourse, this is in addition to the screening effect of charges of the charged residues at the catalytic site of the enzyme.

I would like to recommend you two papers published in Journal of Chromatography 08/2006; 1121(1):129-39 and Comptes Rendus de l'Academie Bulgare des Sciences. 56(4)/2003: 81-85.