Introduction
Pressure Cycling Technology (PCT) has been proven to accelerate enzymatic protein digestion. The positive effect of PCT on trypsin digestion is well established [1-4] for improved sequence coverage, higher recovery and significantly reduced digestion times. Not only has PCT been shown to accelerate and improve digestion in solution, but it can also accelerate in-gel trypsin digestion [4, 5]. Additionally, the enhancing effect of PCT on the activity of several other enzymes, including Proteinase K, PNGase F, chymotrypsin and lysozyme has been reported [6-10].

Introduction
Pressure Cycling Technology (PCT) has been proven to accelerate enzymatic protein digestion. The positive effect of PCT on trypsin digestion has been demonstrated by several laboratories [1, 2, 3] who have reported improved sequence coverage, higher recovery and significantly reduced digestion times when the trypsin reactions were carried out under pressure. Not only has PCT been shown to accelerate and improve digestion in solution, but it can also accelerate in-gel trypsin digestion [4, 5]. Additionally, the enhancing effect of PCT on the activity of several other enzymes, including Proteinase K, PNGase F, Lys-C and lysozyme has been reported [6, 7, 8, 9].

Introduction
Pressure cycling technology (PCT) has been proven to accelerate enzymatic protein digestion. For example, the effect of PCT on trypsin digestion has been demonstrated by several laboratories. They report that digestion times can be reduced from hours to minutes [1, 2]. Not only has PCT been shown to accelerate and improve protein digestion in solution, but it also can accelerate the digestion by trypsin of proteins in polyacrylamide gel slices [3]. Additionally, the enhancing effect of PCT on the activity of several other enzymes, including Proteinase K, PNGase F, and Lys-C, has been reported [4, 5, 6]. It is thought that PCT may act synergistically with other protein denaturants, such as organic solvents and elevated temperature, to help maintain substrates in a denatured state leading to more exposure of enzyme target sites which results in better cleavage,. Here we report the enhanced effect by PCT on the activity of the enzyme lysozyme. Lysozyme acts to hydrolyze peptidoglycans found in bacterial cell walls. This enzyme is frequently used for bacterial cell lysis prior to extracting DNA or proteins from bacteria. We also propose an alternate or additional mechanism by which PCT may enhance the activity of lysozyme.

Introduction
The positive effect of Pressure Cycling Technology (PCT) on trypsin digestion is well established [1-6], and has been shown to result in improved sequence coverage, higher recovery and significantly reduced digestion times. Additionally, the enhancing effect of PCT on the activity of several other enzymes, including Lys-C, Proteinase K, PNGase F, chymotrypsin and lysozyme has been reported [7-13].

Introduction
Pressure Cycling Technology (PCT) has been proven to accelerate enzymatic protein digestion. The positive effect of PCT on trypsin digestion is well established for improved sequence coverage, higher recovery and significantly reduced digestion times [1-5]. Additionally, the enhancing effects of PCT on the activity of other enzymes, including Proteinase K, PNGase F, Glu-C, Lys-C, and lysozyme have been reported [6-12].

Pressure induces protein denaturation, but the pressure-perturbed proteins assume conformational forms that are different from those caused by thermal or chemical treatment [13]. Pressure-induced denaturation of the substrate proteins leads to better enzyme access to previously inaccessible target sites. This, in turn, results in improved and accelerated digestion, as long as the level of pressure that is applied is below the level at which the enzyme itself is denatured and inactivated. In addition, under certain conditions, hydrostatic pressure can have a positive effect on enzyme activity, apparently independent of substrate conformation.

Here we report that PCT can increase specific chymotrypsin activity and accelerate the digestion of model proteins in solution. The goal of this work is to examine the effect of PCT on chymotrypsin activity and to provide the user with the best set of starting conditions for pressure-enhanced chymotrypsin digestion.