Effect of high pressure on the heat activation in vivo of trehalase in the spores of Phycomyces blakesleeanus.

The effect of pressure on the heat activation in vivo of trehalase in the spores of Phycomyces blakesleeanus has been investigated in order to obtain information about the molecular mechanism of the activation. For a protein conformational change directly induced in the enzyme by the heat treatment an upward shift with about 2-6 K/1000 atm (1.013 X 10(5) kPa) is to be expected in the moderate high-pressure region. On the other hand, for a phospholipid phase transition causing the activation, a continuous upward shift with about 20 K/1000 atm is to be expected. For trehalase activation we find a continuous upward shift of the activation temperature with about 5-9 K/1000 atm. The denaturation of trehalase, which occurs at slightly higher temperatures, is influenced by pressure completely as expected for a protein conformational change. The application of high pressure during spore heat activation makes it possibe to break the dormancy of the spores without concomitant activation of trehalase.