Phenylmethanesulfonyl fluoride (PMSF) is a widely used serine protease inhibitor, effective against such enzymes as chymotrypsin, thrombin, and trypsin. PMSF acts as an inhibitor via sulfonation of the hydroxyl residues of serine residues at the reactive sites of serine proteases.

PMSF is often used in lysis buffer to assist in preserving proteins of interest during protein isolation and sample preparation, by inhibiting proteases that would otherwise degrade proteins after cell or tissue lysis. PMSF is unstable in aqueous media. Thus stock solutions of PMSF are generally prepared in anhydrous organic solvents (e.g. 100% ethanol, or anhydrous isopropanol) prior to use in aqueous media.

Noted general features and benefits of PMSF include the following:

• Inhibits serine proteases such as trypsin and chymotrypsin
• Also inhibits cysteine proteases (reversible by reduced thiols) and mammalian acetylcholinesterase
• Not as effective or as toxic as DFP
• Effective concentration 0.1-1 mM
• Half-life = 1 hr. at pH 7.5

Phenylmethanesulfonyl fluoride has been used in following applications:

• cell fractionation.
• used as a supplement in nuclear protein extraction.
• inhibitor of cholesterol esterase (CE) and pseudocholinesterase (PCE).
• used for the collection of blood prior to centrifugation to quantify plasma ANP levels.

Administration of PMSF produces analgesia unrelated to its anticholinesterase effect, and prolongs the analagesic effect of centrally administered β-endorphin.