Hi there,

Normally activity for liquid solution is expressed as U/mL. If this is expressed in U/g you should also have in hands the protein concentration of the samples in g/L in order to work the whole thing out... As far as I know U/g refers to U per gram of protein.

The activities are U/g of the solution.  Without knowing exactly what you are trying to  digest, Because of the wide range of assay methods used, I would recommend testing the proteases at  0.1% and 1% w/w addition to see if you get the desired results.  Best of luck.

Dear Alja,

I agree with Dominique;  protease activity is generally expressed in U/mL.

In case the activity is expressed in U/g; you should measure the volume of 1 gram solution to find the ratio between g/mL such that you can convert the activity from  U/g to U/mL.

Attached please find a paper that researched a  number of theses proteases.

The following are the title and the paper abstract for quick look.

Characterization of the Proteolytic Activity of Commercial

Proteases and Strained Ruminal Fluid1,2

N. D. Luchini, G. A. Broderick3, and D. K. Combs

J. Anim. Sci. 1996. 74:685–692

ABSTRACT: The objective of this research was to formulate a mixture of commercial proteases that would mimic the rate and extent of protein degradation

obtained using strained ruminal fluid. The proteolytic activity of strained ruminal fluid and several commercial proteases was characterized using 13 L-amino acid p-nitroanilides as artificial substrates.

A mixture of Streptomyces griseus protease, chymotrypsin, and proteinase K at .042, 2.5, and .5 enzyme units/mL, respectively, was similar to the activity of strained ruminal fluid against the same artificial substrates. However, degradative activities were different in incubations with feed proteins as substrates. The rates of degradation of expeller soybean meal, solvent soybean meal, and casein were

.08, .05, and .08/h, respectively, using the enzyme mixture and .03, .15, and .24/h using strained ruminal fluid. A second experiment compared degradativeactivity of S. griseus protease at .066 enzyme units/ mL, ficin at .5 enzyme units/mL, and a mixture of trypsin, carboxypeptidase B, chymotrypsin, and carboxypeptidase

A at 116.6, .5, 2.5, and .5 enzyme units/ mL, respectively. Protein degradation rates obtained with strained ruminal fluid were two to six times faster than those obtained with the enzyme mixtures. A third experiment compared the degradability of 15

feed proteins with the mixture of trypsin, carboxypeptidase B, chymotrypsin and carboxypeptidase A to that with strained ruminal fluid. Degradation rates obtained

using strained ruminal fluid ranged from .007 to .217/h; degradation rates using the enzyme mixture ranged from .010 to .079/h and were lower ( P = .004) than with strained ruminal fluid. Overall, the experiments indicated that the commercial enzymes tested did not mimic the protein degradative activity of strained ruminal fluid.

Hoping this will be helpful,

Rafik

To clarify my answer.  Commercial industrial enzyme activities are always expressed in u/g.  The reason for this is simple.  Most industrial enzyme products cannot be reliably pipetted because they contain significant amounts of protein, glycerol, salt sugar, and other preservatives and tend to be highly viscous.  While this may not be a problem in academic research, when you are selling enzymes, the buyer and seller want to get the same activity.  Using U/g allows much higher lab-to-lab reproducibility.  Dried industrial proteases contain a significant amount of non-protease material, so again the need for u/g solid.  The most important thing is to know what you're working with and what is in it.

Thank you all for your contributions and to Alja for raising this question. Permit me Alja to use your platform to raise similar question. I am also new to working with enzymes and will need some clarifications. My research is in the area of meat tenderization, so I need to add (for example, papain in powdered form) to deionized water and then dip my sample into solution and marinate for a period of time. My question is, does 1% enzyme concentration means "1 g of the enzyme powder per 100 g of my sample"? Or should I express this percentage in terms of the volume of deionized water such that "1 g of enzyme powder per 100 mL of deionized water (w/v)? 

My plan is, once I figure out the amount of papain powder that gives the best result I will use the declared activity on the papain product (in U/g of enzyme solid) to calculate the equivalent activity for that amount of enzyme. is this the right approach?

Please, your comments and feedbacks will be highly appreciated. Thanks

Hi, Everyone,

Its is a nice discussion.

Could anyone help me out in order to know about the amylase, protease and lipase daily requirement for healthy adult man/women? I shall be thankful to you. Please suggest daily requirement in EU/day. ?

Thank you.