Inhibition of serine proteases by peptidyl fluoromethyl ketones

Journal Article · Tue Jul 01 00:00:00 EDT 1986 · Biochemistry; (United States)

DOI:https://doi.org/10.1021/bi00361a005· OSTI ID:6602524

Imperiali, B; Abeles, R H

Peptidyl fluoromethyl ketones that are specific inhibitors of the serine proteases ..cap alpha..-chymotrypsin and porcine pancreatic elastase were synthesized. By analogy with the corresponding aldehydes it is assumed that the fluoromethyl ketones react with the ..gamma..-OH group of the active site serine to form a stable hemiacetal. /sup 19/F NMR studies of the chymotrypsin-bound trifluoromethyl ketone inhibitors Ac-Leu-ambo-Phe-CF/sub 3//sup 1/ and Ac-ambo-Phe-CF/sub 3/ clearly indicate that the carbonyl carbon is tetrahedral at the active site of the enzyme. The inhibitor is bound as either the stable hydrat or the hemiacetal, involving the active site serine. The effect of varying the number of amino acid residues in the peptidyl portion of the inhibitor and the number of fluorines in the fluoromethyl ketone moiety is examined. In the series of trifluoromethyl ketone elastase inhibitors, the lowering of K/sub i/ concomitant with the change from a dipeptide analogue to a tetrapeptide analogue correlates well with the variation in V/K for hydrolysis of the corresponding amide substrates. This trend is indicative of the inhibitors acting as transition-state analogues. In addition to chain length, the number of fluorine substituents also affects the K/sub i/. In the case of chymotrypsin, the K/sub i/ for Ac-Leu-ambo-Phe-CF/sub 3/ is 30-fold lower than that for Ac-Leu-ambo-Phe-CF/sub 2/H. With elastase this trend is not as profound. In all cases, however, the difluoro- and trifluoromethyl ketones are better inhibitors than the monofluoromethyl and nonfluorinated analogues. This improvement must be associated with both the degree of hydration of the fluoromethyl ketones and the significant effect that fluorine substitution has on lowering the first pK/sub a/ of the hemiacetal hydroxyl. The monofluoromethyl ketone inhibitor of chymotrypsin, Ac-Leu-ambo-Phe-CFH/sub 2/, is a weak competitive inhibitor.

• Research Organization: Brandeis Univ., Waltham, MA (USA)
• OSTI ID: 6602524
• Journal Information: Biochemistry; (United States), Journal Name: Biochemistry; (United States) Vol. 25:13; ISSN BICHA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
AMINO ACIDS
BIOCHEMICAL REACTION KINETICS
CARBOXYLIC ACIDS
FLUORINE 19
FLUORINE ISOTOPES
HYDROXY ACIDS
ISOTOPES
KINETICS
LABELLED COMPOUNDS
LIGHT NUCLEI
MAGNETIC RESONANCE
NUCLEAR MAGNETIC RESONANCE
NUCLEI
ODD-EVEN NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC FLUORINE COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
REACTION KINETICS
RESONANCE
SERINE
STABLE ISOTOPES
STRUCTURAL CHEMICAL ANALYSIS