The biochemistry of barley

Briggs, D. E.

doi:10.1007/978-94-009-5715-2_4

Cited by 1 publication

(2 citation statements)

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“…6). Therefore, α-and β-amylases are not present and α-glucosidase must be the only enzyme to hydrolytically degrade starch in cells of S. cataractae, although many reports have demonstrated that α-and β-amylases play essential roles in starch digestion (Briggs, 1978;Enari & Sopanen, 1986;Scheidig et al, 2002;Lu & Sharkey, 2004;Niittylä et al, 2004;Sean et al, 2004). This is supported by the finding that glucose was the sole product of amylopectin digestion with BS or LS.…”

Section: α-Glucosidase From the Moss Scopelophila Cataractaementioning

confidence: 99%

“…The plant α-glucosidases readily hydrolyze malto-oligosaccharides (Matsui et al, 1978;Chiba et al, 1979;Yamasaki & Konno, 1991;Konishi et al, 1992;Eksittikul et al, 1993;Yamasaki et al, 1996;2005). Some authors have reported that reserve starch is hydrolyzed into glucose by the concerted action of α-and β-amylases, debranching enzyme and α-glucosidase (Briggs, 1978;Enari & Sopanen, 1986). On the other hand, α-glucosidases from barley (Sun & Henson, 1990), malt (Sissons & MacGregor, 1994), millet (Yamasaki et al, 1996), and pea (Sun et al, 1995) degrade intact starch granules by themselves.…”

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confidence: 99%

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A novel alpha-glucosidase from the moss Scopelophila cataractae.

Yamasaki¹,

Nakashima²,

Konno³

2007

Acta Biochim Pol

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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 alpha-glucosidase (EC 3.2.1.20) in BS and LS hydrolyzed amylopectin. The K(m) value of BS for maltose was 0.427. The K(m) 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 alpha-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 K(m) 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 alpha-glucosidases. The two enzymes also hydrolyzed beta-limit dextrin, which has many alpha-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 alpha-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 alpha-glucosidase. These results show that alpha-glucosidases should be capable of complete starch digestion by themselves in cells of S. cataractae.

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