Solute radical inactivation of the sulfhydryl enzyme papain: sensitization and protection

Journal Article · Wed Aug 01 04:00:00 EDT 1973 · Can. J. Chem., v. 51, no. 15, pp. 2443-2447

DOI:https://doi.org/10.1139/v73-365· OSTI ID:4423118

Gaucher, G M; Mainman, B L; Armstrong, D A

Particularly pure N/sub 2/O-purged papain solutions (2 x 10/sup -5/ M; pH 6.8) were irradiated at 0 deg C for different times with /sup 69/Co gamma rays, in the presence of 10 to 30 mM solutions of acetate, isobutanol, and thiocyanate. In comparison to OH radicals, these solute radicals substantially enhanced papain inactivation. Calculated inactivation probabilities per papain- radical reaction (i.e., 0.43 for OH and 1.00 for solute radicals) support this finding. In situ protection of both N/sub 2/-purged and N/sub 2/O saturated papain solutions by cysteine was found to occur only at cysteine: papain molar ratios above 15: 1, while below this ratio substantial sensitization occurred, reaching a maximum at a 2: 1 ratio. This enhanced inactivation of papain at low cysteine concentrations is primarily repairable in nature, and probably due to CysSattack on papain's active site sulfhdryl. Only at relatively high cysteine: papain ratios (>30) can protection be ascribed to radical scavenging. (auth)

• Research Organization: Univ. of Calgary, Alberta
• NSA Number: NSA-29-002831
• OSTI ID: 4423118
• Journal Information: Can. J. Chem., v. 51, no. 15, pp. 2443-2447, Journal Name: Can. J. Chem., v. 51, no. 15, pp. 2443-2447; ISSN CJCHA
• Country of Publication: Canada
• Language: English

Related Subjects

*ACETATES-- RADIOSENSITIVITY EFFECTS
*BUTANOLS-- RADIOSENSITIVITY EFFECTS
*CYSTEINE-- RADIOSENSITIVITY EFFECTS
*PAPAIN-- BIOLOGICAL RADIATION EFFECTS
*THIOCYANATES-- RADIOSENSITIVITY EFFECTS
GAMMA RADIATION
INACTIVATION
N40300 --Chemistry--Radiation Chemistry
N48110* --Life Sciences--Radiation Effects on Biochemicals-- In-Vitro
PHOTON BEAMS
SCAVENGING