Hi Nwonuma, it depends on what enzymes you are measuring.

Serine proteinases of the coagulation and complement cascade are, to my knowledge, minimally affected by hemoglobin or free Fe+2/Fe+3.

Dehydro/reductases will be affected by the redox potential of serum.

I have had to worry about such problems on many projects.  Dr. Stfansson is absolutely correct:  "It depends on what enzymes you are measuring".  However, in my experience, I often found background (contaminating) enzyme problems in just about every biochemical evaluation involving serum/plasma.  Either some contaminating enzyme increases the background, or equally likely that some inhibitor is elevated, and sometimes both can happen.

So, my strong suggestion is to run empirical control experiments.  This will be truly the only way to be certain for your specific assay.  There are several styles of controls to choose from. 

One option:  You can make a prep of washed red cells, lyse them intentionally, and use that as input sample, representing the 'worst case scenario'.  But you must remember that red cells lysed in isolation do not truly mimic hemolyzed sample, because the released proteins surely effect other cells in the whole sample, especially platelets, which then further alter the serum content.

Another option:  take parallel samples from the same subject and compare them.  Use a very clean serum sample, and then another sample that you intentionally 'abuse' to induce hemolysis (maybe something like vortexing aggressively or shaking the tube vigorously -- anything that you would never think of doing to a usual blood sample), and compare the two samples on your enzyme assay.  You can even make mixtures of the good and hemolyzed serum at different ratios, to get an idea of how the extent of hemolysis appears to effect your specific assay. 

Dear College:In my experience: In according to standarization the effect of hemolysis  in my laboratory(CAP) ,I quantify the free serum hemoglobin in the sample and  I admit up tp 0.6 g/L  serum hemoglobin.