Catalase activity in human whole blood was measured by disappearance of H2O2 at

Question

Catalase activity in human whole blood was measured by disappearance of H2O2 at 240 nm in a 3 mL assay. The extinction coefficient at 240 nm is 43.6 M-1 cm-1. show all work

a) 50 L of whole blood was added to a 3 mL assay. Red cells were immediate lysed, releasing catalase. A rate of 0.316 min-1 was measured. Calculate the catalase activity (Units) per mL of while blood.

b) Catalase is contained in red cells, but not in plasma. Blood hematocrit (%red cells in blood) is 50%. What is the catalase activity in packed red cells?

Explanation / Answer

The general formula for enzyme activity from rate of change of absorbance is:

rate of change of abs per minute X (total reaction volume/(MA/1000) X 1/(volume sample used)

By including the MOLAR absorption and 1000/sample volume you end up with international units per 1 ml which are common units.

Catalase activity = 0.316*3ml*1000/ 43.6*50

= 0.43

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