Leukotriene A4 hydrolase in the human B-lymphocytic cell line Raji: indications of catalytically divergent forms of the enzyme.
Leukotriene A4 hydrolase was purified 1400-fold, with an approximate yield of 25%, to apparent homogeneity from the human B-lymphocytic cell line Raji. The purification included ammonium sulfate precipitations followed by anion exchange, hydrophobic interaction, and molecular exclusion fast protein liquid chromatography. Kinetic properties at 2 degrees C varied between different enzyme preparations. Two patterns were observed, one with a Km of about 12 microM and Vmax of about 1.1 mumol LTB4/mg protein/min which correlated well with the properties of the human leukocytic LTA4 hydrolase. In other enzyme preparations a higher catalytic activity was observed. These enzyme batches did not obey Michaelis-Menten kinetics but were compatible with a mixture of enzymatic species. Heat treatment (60 degrees C) led to a time-dependent decline in catalytic activity. However, certain enzyme preparations contained a subfraction of enzymatic activity which was more resistant to heat treatment, yielding a biphasic inactivation pattern. It is thus suggested, on the basis of the kinetic properties and the heat-inactivation pattern, that these enzyme preparations contained an addition form of LTA4 hydrolase.
Odlander
B
B
Department of Physiological Chemistry, Karolinska Institutet, Stockholm, Sweden.
Claesson
H E
HE
Bergman
T
T
Rådmark
O
O
Jörnvall
H
H
Haeggström
J Z
JZ
D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D001402:B-Lymphocytes / Q000201:enzymology*; D004591:Electrophoresis, Polyacrylamide Gel; D004851:Epoxide Hydrolases / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D006801:Humans; D007525:Isoelectric Focusing; D007700:Kinetics; D008969:Molecular Sequence Data; D014407:Tumor Cells, Cultured
D000596:Amino Acids; D004851:Epoxide Hydrolases; C043134:leukotriene A4 hydrolase