What Are the Factors that Affect the Activity of Proteinase K ?

Proteinase K is a popular broad-spectrum protease,which be considered the most active protease. Proteinase K has excellent stability and can maintain high activity under high temperature, high salt, high pH or some common inhibitors, but this don't mean that the activity of proteinase K is not affected by external factors.

The activity of Proteinase K be affected by pH.

Proteinase K is active in a wide pH range (4~12.5), but it is also affected by pH. Its catalytic activity remains stable in the range of pH 6-10, and increases greatly in the range of pH 8-10. At pH 3.5-9.0, the three-dimensional structure of proteinase K molecule is not sensitive to changes in pH, but irreversible changes will occur in overacidic and overalkaline environments.

The activity of Proteinase K be affected by temperature.

Proteinase K retains the highest activity of over 80% in the range of 20 ℃-60 ℃, and the enzyme activity is maximum at 37 ℃. It can be partially inactivated by holding at 65 ℃ for 10min-15min, and heating at 95 ℃ for 10 min will cause complete inactivation of proteinase K.

The activity of Proteinase K be affected by Ca²⁺

Natural proteinase K binds two Ca²⁺. Removaling Ca²⁺ will reduce the thermal stability and a certain degree of substrate affinity of proteinase K , but has no effect on its catalytic activity of the enzyme. Natural and Ca²⁺depleted proteinase K has similar structural properties; some hydrogen bonds and salt bridges in proteinase K play a key role in maintaining the conformation around the two Ca²⁺ sites.

The activity of proteinase K be Effected by activators and inhibitors.

Proteinase K can still maintain stability and vitality in chelating agent EDTA, mercapto reagent, p-chloromercuric benzoic acid (PCMB), or tosyl-phenylalanine chloromethyl ketone ( TPCK).  And denaturants such as urea and SDS can improve its catalytic activity. However, proteinase K belongs to the class of serine proteases, and its activity can be inhibited by benzylsulfonyl fluoride (PMSF) or diisopropylfluorophosphate (DFP).

In summary, pH, temperature, Ca2+, activators and inhibitors are the main factors that affect the activity of proteinase K.

Related Links: Proteinase K