A novel α-glucosidase from the moss Scopelophila cataractae
Languages of publication
Scopelophila cataractae is a rare moss that grows on copper-containing soils. S. cataractae protonema was grown on basal MS medium containing copper. A starch-degrading activity was detected in homogenates of the protonema, after successive extraction with phosphate buffer and buffer containing 3 M LiCl. Buffer-soluble extract (BS) and LiCl-soluble extract (LS) readily hydrolyzed amylopectin to liberate only glucose, which shows that α-glucosidase (EC 22.214.171.124) in BS and LS hydrolyzed amylopectin. The Km value of BS for maltose was 0.427. The Km value of BS for malto-oligosaccharide decreased with an increase in the molecular mass of the substrate. The value for maltohexaose was 0.106, which is about four-fold lower than that for maltose. BS was divided into two fractions of α-glucosidase (BS-1 and BS-2) by isoelectric focusing. The isoelectric points of these two enzymes were determined to be 4.36 (BS-1) and 5.25 (BS-2) by analytical gel electrofocusing. The two enzymes readily hydrolyzed malto-oligosaccharides. The two enzymes also hydrolyzed amylose, amylopectin and soluble starch at a rate similar to that with maltose. The two enzymes readily hydrolyzed panose to liberate glucose and maltose (1 : 1), and the Km value of BS for panose was similar to that for maltotriose, whereas the enzymes hydrolyzed isomaltose only weakly. With regard to substrate specificity, the two enzymes in BS are novel α-glucosidases. The two enzymes also hydrolyzed β-limit dextrin, which has many α-1,6-glucosidic linkages near the non-reducing ends, more strongly than maltose, which shows that they do not need a debranching enzyme for starch digestion. The starch-degrading activity of BS was not inhibited by p-chloromercuribenzoic acid or α-amylase inhibitor. When amylopectin was treated with BS and LS in phosphate buffer, pH 6.0, glucose, but not glucose-1-phosphate, was detected, showing that the extracts did not contain phosphorylase but did contain an α-glucosidase. These results show that α-glucosidases should be capable of complete starch digestion by themselves in cells of S. cataractae.
- Awdeh ZL, Williamson AR, Askonas BA (1968) Isoelectric focusing in polyacrylamide gel and its application to immunoglobulines. Nature (London) 219: 66-67.
- Briggs DE (1978) The biochemistry of barley. In Barley (Briggs DE, ed) pp 89-173, Chapman & Hall, London.
- Chiba S, Kanaya K, Hiromi K, Shimomura T (1979) Substrate specificity and subsite affinities of buckwheat α-glucosidase. Agric Biol Chem 43: 237-242.
- Dahlqvist A (1961) Determination of maltase and isomaltase activities with a glucose-oxidase reagent. Biochem J 80: 547-551.
- Eksittikul T, Svendsby O, Yazmaguchi H, Iizuka M, Minamimura N (1993) Thai rice seed α-glucosidase and its specificity. Biosci Biotechnol Biochem 57: 319-321.
- Enari TM, Sopanen T (1986) Mobilisation of endospermal reserves during the germination of barley. J Inst Brew 92: 25-31.
- Fawcett JS (1968) Isoelectric fractionation of proteins on polyacrylamide gels. FEBS Lett 1: 81-82.
- Henson CA, Sun Z (1995) Barley seed α-glucosidases: Their characteristics and roles in starch degradation. In Enzymatic degradation of insoluble carbohydrates (Saddler JN, Penner MH, eds), pp 51-58, American Chemical Society, Washington, DC.
- Konishi Y, Kitazato S, Nakatani N (1992) Partial purification and characterization of acid and neutral α-glucosidases from preclimacteric banana pulp tissues. Biosci Biotechnol Biochem 56: 2046-2051.
- Konno H, Tsumuki H (1993) Purification of a β-galactosidase from rice shoots and its involvement in hydrolysis of the natural substrate in cell walls. Physiol Plant 89: 40-47.
- Lowry OH, Rosebrough NJ, Farr AL, Randall RJ (1951) Protein measurement with the Folin phenol reagent. J Biol Chem 193: 265-275.
- Lu Y, Sharkey TD (2004) The role of amylomaltase in maltose metabolism in the cytosol of photosynthetic cells. Planta 218: 466-473.
- Matsui H, Chiba S, Shimomura T (1978) Substrate specificity of an α-glucosidase in sugar beet seed. Agric Biol Chem 42: 1855-1860.
- Murashige T, Skoog F (1962) A revised medium for rapid growth and bio assays with tobacco tissue cultures. Physiol Plantarum 15: 473-497.
- Niittylä T, Messerli G, Trevisan M, Chen J, Smith AM, Zeeman SC (2004) A previously unknown maltose transporter essential for starch degradation in leaves. Science 303: 87-89.
- Papadopoulos NM, Hess WC (1960) Determination of neuraminic (sialic) acid, glucose, and fructose in spinal fluid. Arch Biochem Biophys 88: 167-171.
- Scheidig A, Fröhlich A, Schulze S, Lloyd JR, Kossmann J (2002) Downregulation of a chloroplast-targeted β-amylase leads to a starch-excess phenotype in leaves. Plant J 30: 581-591.
- Sean EW, Weber APM, Sharkey TD (2004) Maltose is the major form of carbon exported from the chloroplast at night. Planta 218: 474-482.
- Sissons MJ, MacGregor AW (1994) Hydrolysis of barley starch granules by α-glucosidases from malt. J Cereal Sci 19: 161-169.
- Somogyi M (1952) Notes on sugar determination. J Biol Chem 195: 19-23.
- Sun Z, Henson CA (1990) Degradation of native starch granules by barley α-glucosidase. Plant Physiol 94: 320-327.
- Sun Z, Duke SH, Henson CA (1995) The role of pea chloroplast α-glucosidase in transitory starch degradation. Plant Physiol 108: 211-217.
- Yamasaki Y (2003) β-Amylase in germinating millet seeds. Phytochemistry 64: 935-939.
- Yamasaki Y, Suzuki Y (1980) Two forms of α-glucosidase from sugar-beet seeds. Planta 148: 354-361.
- Yamasaki Y, Konno H (1991) Purification and properties of α-glucosidase from suspension-cultured sugar-beet cells. Phytochemistry 30: 2861-2863.
- Yamasaki Y, Suzuki Y, Ozawa J (1977) Three forms of glucosidase and a glucoamylase from Aspergillus awamori. Agric Biol Chem 41: 2149-2161.
- Yamasaki Y, Konno H, Mashima H (1996) Purification and properties of α-glucosidase from millet seeds. Phytochemistry 41: 703-705.
- Yamasaki Y, Fujimoto M, Kariya J, Konno H (2005) Purification and characterization of an α-glucosidase from germinating millet seeds. Phytochemistry 66: 851-857.
Publication order reference