CRY-J-2, A MAJOR ALLERGEN OF JAPANESE CEDAR POLLEN, SHOWS POLYMETHYLGALACTURONASE ACTIVITY
CRY-J-2, A MAJOR ALLERGEN OF JAPANESE CEDAR POLLEN, SHOWS POLYMETHYLGALACTURONASE ACTIVITY
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DOI：
10.1111/j.1398-9995.1995.tb01183.x
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发表时间：
1995-06-01
期刊：
影响因子：
12.4
通讯作者：
KURIMOTO, M
中科院分区：
文献类型：
--
作者：
OHTSUKI, T;TANIGUCHI, Y;KURIMOTO, M
我们研究了日本雪松（柳杉）花粉的主要过敏原Cry j 2的多聚半乳糖醛酸酶活性，因为Cry j 2的cDNA的核苷酸序列与番茄多聚半乳糖醛酸酶的核苷酸序列显示出显着的同源性。多聚半乳糖醛酸酶是一种通过水解多聚半乳糖醛酸（PGA）而优先降解PGA的酶。Cry j 2对PGA无作用，但对果胶和甲酯化PGA有剂量依赖性的脱果胶作用。Cry j 2的底物特异性与尼日尔曲霉多聚半乳糖醛酸酶不同。当PGA的甲酯化度为50%~ 60%时，Cryj 2的解聚活性最大.聚半乳糖醛酸酶对PGA的酶活最高，且酶活随酯化程度的增加而降低。有趣的是，Cry j 2的果胶解聚活性是由于水解，而不是裂解酶，其通过β-消除分裂糖苷键的活性，因为通过测量反应混合物中235 nm处的吸光度没有发现不饱和的糖醛酸苷。抗Cry j 2抗体可显著抑制该酶活性。这些结果表明，Cry j 2可能具有多甲基半乳糖醛酸酶活性，正如von Neukom在1963年所假设的，尽管这种活性的存在尚未得到证实。
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 to 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.