Enzyme‐Catalyzed Reactions as Influenced by Inert Gases at High Pressures

Abstract

The activities of tyrosinase, invertase, trypsin and chymotrypsin were studied after exposure to one or more of the following high-pressure inert gases: N20 at 600 psig or NI or Ar each at 5000 psig. Exposure to high-pressure nitrogen or argon failed to significantly inhibit the rate of tyrosinase activity in fluid systems. However, the rates of tyrosinase-catalyzed reactions in shell-cast gelatin gels were significantly depressed by exposure to high-pressure nitrogen, and even more so by high-pressure nitrous oxide. This inhibition proved to be oxygen dependent and reversible. Pressurization experiments with invertase, trypsin and chymotrypsin indicated that high-pressure N20 did not significantly inhibit these enzymes. This fends support to the hypothesis that highpressure inert gases inhibited tyrosinase activity in nonfluid systems by decreasing the availability of oxygen, rather than by physically altering the enzyme. It must be concluded that there is little hope that the enzymes in food systems can be effectively inhibited by brief exposure to inert gases at pressures of 5000 psig or less.

Effects of high pressure argon treatments on the quality of fresh-cut apples at cold storage

“…Fujii et al (2002) reported that addition of argon accelerated the inactivation of Bacillus cereus spores at 20 C under the pressure of 600 MPa due to argon clathrate hydrates information. Behnke (1969) suggested that high pressure inert gases inhibit tyrosinase in non-fluid (i.e. gelatin) systems by decreasing oxygen availability.…”

Extension of mushroom shelf-life by ultrasound treatment combined with high pressure argon

“…Behnke et al (1969) also demonstrated that high pressure inert gases inhibited tyrosinase systems by decreasing oxygen availability rather than by physical alteration of the enzyme. When noble gases dissolve in water, enzymatic reactions are inhibited, resulting in restrained vegetable metabolism (Zhang et al, 2008).…”

Effects of Argon Enriched Low‐Oxygen Atmospheres and of High‐Oxygen Atmospheres on the Kinetics of Polyphenoloxidase (PPO)

“…Partly purified tyrosinase (PPO) was inhibited by noble gases including argon (Doebbler and others 1967; Behnke and others 1969; Spencer and others 1998; Zhang and others 2001). Ebert and Hornsey (1958) proposed that inert gases compete with oxygen for cellular sites; however, inhibition by noble gases was also found for some non‐oxygen dependant enzymatic reactions (Behnke and others 1969) and direct competition between oxygen and the inert gas did not appear to occur for an oxygenase (Doebbler and others 1967).…”

“…Partly purified tyrosinase (PPO) was inhibited by noble gases including argon (Doebbler and others 1967; Behnke and others 1969; Spencer and others 1998; Zhang and others 2001). Ebert and Hornsey (1958) proposed that inert gases compete with oxygen for cellular sites; however, inhibition by noble gases was also found for some non‐oxygen dependant enzymatic reactions (Behnke and others 1969) and direct competition between oxygen and the inert gas did not appear to occur for an oxygenase (Doebbler and others 1967). Schreiner (1968) proposed that changes in enzymatic activity might be the result of interactions between the noble gases and the enzyme, but this theory was refuted by Behnke and others (1969) who concluded that high‐pressure inert gases inhibited tyrosinase activity in nonfluid systems by decreasing the availability of oxygen rather than by physically altering the enzyme.…”

“…Partly purified tyrosinase (PPO) was inhibited by noble gases including argon (Doebbler and others 1967;Behnke andothers MS 20100629 Submitted 6/8/2010, Accepted 10/21/2010. Authors are with Food Science Research Centre, Dept.…”