{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

J._Biol._Chem.-1944-Sizer-461-73 - Copy

J._Biol._Chem.-1944-Sizer-461-73 - Copy - TEMPERATURE...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
TEMPERATURE ACTIVATION AND INACTIVATION OF THE CRYSTALLINE CATALASE-HYDROGEN PEROXIDE SYSTEM BY IRWIN W. SIZER (From the Department of Biology and Biological Engineering, Massachusetts Institute of Technology, Cambridge) (Received for publication, April 22, 1944) The many studies on the action of temperature changes upon the cata- lase-HzOz system have been reviewed by Zeile (25). Some workers have found that this reaction, like many other enzyme-catalyzed reactions, increases with temperature in a,ccordance with the Arrhenius equation (cf. Sizer (16)) with corresponding activation energies varying from 2600 to 6200 calories per gm. molecule. Others (cf. Williams (24)) have found that, the activation energy changes both with temperature and pH, while Morgulis et al. (12) came to the conclusion that the optimum temperature for catalase action is at 2” instead of 40-50” as reported by others. Above the optimum temperature the rate of catalase inactivation increases rapidly with temperature, and the corresponding activation energies are between 30,000 and 50,000 calories per gm. molecule. Part of the difficulty in procuring significant data on the effects of temperature on the catalase- Hz02 system arises from the fact that, due to its strong oxidizing power, Hz02 is a very toxic substance and rapidly inactivates the catalase. To overcome this major difficulty in the present investigation very dilute peroxide solutions at optimum pH have been employed, and manometric data on oxygen evolution from peroxide during only the initial few minutes of the reaction have been used, during which time the destruction of the enzyme by the dilute peroxide solution is almost negligible. Another diffi- culty has been that all previous workers have utilized impure enzyme prep- arations from a variety of sources; it seemspossible that such impurities have exerted some influence on the kinetics of the reaction. In this study use has been made of once recrystallized beef liver catalase. The inactiva- tion of catalase by heat has been investigated both in the presence and absence of substrate. Methods The catalase used in these experiments was prepared from beef liver and was once recrystallized according to the method of Sumner and Dounce (21). A saturated solution of crystalline catalase was kept in the refriger- ator and for each series of experiments a suitable dilution of the enzyme 461 by guest, on October 19, 2010 www.jbc.org Downloaded from
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
462 CATSLASE-HYDROGEN PEROXIDE SYSTEM was made. Although several different preparations of crystalline catalase were made from liver, no important difference in their behavior was noticed. The reaction was followed by measuring oxygen evolution from Hz02 with a Warburg-Barcroft manometer, with a reaction vessel having a single side arm. In the cup were placed 1 ml. of suitably diluted catalase, 1 ml. of 0.03 M phosphate buffer, pH 6.9, and in the side arm, 1 ml. of 0.03 M H?Oz.
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

Page1 / 13

J._Biol._Chem.-1944-Sizer-461-73 - Copy - TEMPERATURE...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon bookmark
Ask a homework question - tutors are online