Pepper beta-galactosidase 1 (PBG1) plays a significant role in fruit ripening in bell pepper (Capsicum annuum).
During bell pepper (Capsicum annuum L.) fruit ripening, beta-galactosidase activity increased markedly as compared with other glycosidases. We purified 77.5 kDa exo-1,4-beta-D-galactanase from red bell pepper fruit classified as beta-galactosidase II. A marked decrease in galactose content appeared during fruit ripening, especially in the pectic fraction. The purified enzyme hydrolyzed a considerable amount of galactose residues in this fraction. We isolated bell pepper beta-galactosidase (PBG1) cDNA. This PBG1 protein contained the putative active site, G-G-P-[LIVM]-x-Q-x-E-N-E-[FY], belonging to glycosyl hydrolase family 35. Quantitative RT-PCR revealed that the expression of PBG1 in red fruit was significantly stronger than that from any other tissues. Moreover, expression of PBG1 occurred prior to that of pepper endo-polygalacturonase 1 (PPG1), the major fruit-ripening enzyme. Based on these results, it appears that the hydrolysis of galactose residues in pectic substances is the first event in the ripening process in bell pepper fruit.
Ogasawara
Satoshi
S
Graduate School of Agricultural Sciences, Tohoku University, Sendai, Japan. satoshi-ogasawara@aist.go.jp
Abe
Keietsu
K
Nakajima
Tasuku
T
D002212:Capsicum / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development*; D002241:Carbohydrates / Q000737:chemistry; D002473:Cell Wall / Q000737:chemistry; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000096:biosynthesis / Q000235:genetics; D004591:Electrophoresis, Polyacrylamide Gel; D005638:Fruit / Q000201:enzymology* / Q000254:growth & development*; D006026:Glycoside Hydrolases / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D008958:Models, Molecular; D010368:Pectins / Q000378:metabolism; D011134:Polysaccharides / Q000737:chemistry / Q000378:metabolism; D018749:RNA, Plant / Q000096:biosynthesis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013379:Substrate Specificity; D001616:beta-Galactosidase / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*
D002241:Carbohydrates; D018076:DNA, Complementary; D011134:Polysaccharides; D018749:RNA, Plant; D010368:Pectins; D006026:Glycoside Hydrolases; C066350:exo-1,4-beta-galactanase; D001616:beta-Galactosidase