Because the seeds of most plants, including the seeds of cress, contain a high level of proteases, therefore Purify the enzyme from the seeds of garden cress in several steps, including concentration with ammonium sulfate at a saturation rate of 50-60%. The specific activity of the enzyme reached 61.513 U / mg protein. Then the enzyme was passed through an ion exchange DEAE-cellulose column. The enzyme recorded a specific activity of 132,080 units/mg protein, with a purification fold 2.147, and yield 30.49%. Then gel filtration on a Sephacyl S-200 column. The enzyme recorded specific activity, purification fold and its yield, 660 U/mg protein, 4.1641, 27.72% respectively. The enzyme was characterized by setting the optimum pH and optimum temperature. The enzyme recorded the highest activity at pH 7 and pH stability from 7-8. The enzyme also showed the highest activity at a temperature of 35°C for a period of 15 minutes. The enzyme was also showed stable at a temperature 20-40°C for 15 minutes. The result of the effect of chemical compound on the activity of the enzyme showed that it was not affected by the present of sodium and potassium chloride except in a small percentage at concentration 5,10 mM, but it increase slightly when the enzyme was incubated with calcium chloride, it reached 104,110 and magnesium chloride 110,115 at concentration 5,10 mM, respectively. No effect was shown for thiol compounds such as cysteine at concentration 1,10 mM while it was affected by the presence of chelating agents EDTA. Also studied the effect of the activity of the enzyme purified from cress seeds against the types of positive and negative gram stain, as well as fungi and yeast, the result showed the activity of the enzyme at concentration 10,15 and 20 and that the highest response of the bacteria was at 20 concentration, while, no effect of fungi was shown except at concentration 20.