I am trying to access the GTPase activity of my protein using malachite green kit by sigma. According to the protocol mentioned, after adding malachite it should be incubated for 30min. In 30 minutes, the absorbance for GTP reaction control ( reaction without enzyme) shows an absorbance of 1.3-1.5

For reaction, I am using ultra pure GTP solution by SRL. I checked the O.D of just buffer which is