Cry j 2, a major allergen of Japanese cedar pollen, shows polymethylgalacturonase activity.
We examined Cry j 2, a major allergen of Japanese cedar (Cryptomeria japonica) pollen, for polygalacturonase enzyme activity, since a nucleotide sequence of cDNA of Cry j 2 showed a significant homology with that of tomato polygalacturonase. Polygalacturonase is well known to depolymerize preferentially polygalacturonic acid (PGA) by hydrolysis. However, Cry j 2 did not act on PGA, but was found to depolymerize pectin and methylesterified PGA in a dose-dependent manner. The substrate specificity of Cry j 2 was different from that of polygalacturonase derived from Aspergillus niger. The depolymerizing activity of Cry j 2 reached a maximum at 50%-60% of methylesterification of PGA. In contrast, polygalacturonase showed its maximum activity of PGA, and the activity decreased as the degree of methylesterification increased. Interestingly, the pectin-depolymerizing activity of Cry j 2 was due to a hydrolysis, but not a lyase, activity which splits the glycosidic bonds by beta-elimination, since no unsaturated uronides were found by measurement of absorbance at 235 nm in the reaction mixture. The enzyme activity was markedly inhibited by anti-Cry j 2 antibodies. These results indicate that Cry j 2 probably has polymethylgalacturonase enzyme activity, as postulated by von Neukom in 1963, although existence of this activity has not yet been proven.
Ohtsuki
T
T
Fujisaki Institute, Hayashibara Biochemical Laboratories, Inc, Okayama, Japan.
Taniguchi
Y
Y
Kohno
K
K
Fukuda
S
S
Usui
M
M
Kurimoto
M
M
D000485:Allergens / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004951:Esterification; D006026:Glycoside Hydrolases / Q000378:metabolism*; D006868:Hydrolysis; D010368:Pectins / Q000378:metabolism; D010940:Plant Proteins / Q000378:metabolism* / Q000494:pharmacology; D011058:Pollen / Q000276:immunology*; D011108:Polymers / Q000378:metabolism; D011133:Polysaccharide-Lyases / Q000378:metabolism
D000485:Allergens; C065291:Cry j II protein, Cryptomeria japonica; D010940:Plant Proteins; D011108:Polymers; D010368:Pectins; D006026:Glycoside Hydrolases; C022420:polymethylgalacturonase; D011133:Polysaccharide-Lyases; C023911:pectate lyase; C003181:polygalacturonic acid