Enzyme inhibitors can also irreversibly inactivate enzymes, usually by covalently modifying active site residues. SV40 uses the same protein for inactivating Rb, LT, to inactivate p53. Disinfectants are chemical agents designed to inactivate or destroy microorganisms on inert surfaces. PMSF does not inactivate all serine proteases. Inactivated vaccines are further classified depending on the method used to inactivate the virus. Certain bacteria can produce enzymes called lactonases that can target and inactivate AHLs. The juice is then pasteurized to inactivate remaining natural enzymes and kill micro-organisms. Trypsin may also inactivate other trypsin by cleavage. Antihistamines do not chemically inactivate or prevent the normal release of histamine. Blanching at temperatures or times lower than those recommended may not effectively inactivate all enzymes. Alcohols are effective against a range of microorganisms, though they do not inactivate spores. It is an effective method to inactivate harmful protozoa that form cysts. This process requires immune mechanisms to kill or inactivate the inoculum of the pathogen. The oxidative stress may also inactivate OGG1. Studies have show that many quaternary ammonium compound based disinfectants do not inactivate caliciviruses.