Proteinase from Carica papaya latex was tested on its thermal stability at atmospheric pressure and in supercritical carbon dioxide, near-critical propane and dimethyl-ether. In supercritical carbon dioxide at 300 bar thermal activation of the examined protemase was improved in the comparison to atmospheric pressure. In propane and dimethyl-ether (300 bar) activity of the examined protemase decreased. Influence of compression/expansion cycles on residual activity of the same protemase in supercritical carbon dioxide (300 bar) and 50degreesC was studied, as well. Different ways of transition from supercritical to low-pres sure- state were used which affected residual activity of the protemase. Addition of water in the system increased activity of proteinase from C. papaya, which was incubated in supercritical carbon dioxide for 24 h. Optimum amount of water was found to be between 0.5 and 0.7 g/L. (C) 2004 Elsevier B.V. All rights reserved.