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Differences and similarities in enzymes from the neopullulanase subfamily isolated from thermophilic species

In English

Författare

Summary, in English

Six glycoside hydrolase (GH) family 13 members, classified under the polyspecific neopullulanase subfamily GH13_20 (also termed cyclomaltodextrinase) were analysed. They originate from thermophilic bacterial strains (Anoxybacillus flavithermus, Laceyella sacchari, and Geobacillus thermoleovorans) or from environmental DNA, collected after in situ enrichments in Icelandic hot springs. The genes were isolated following the CODEHOP consensus primer strategy, utilizing the first two of the four conserved sequence regions in GH13. The typical domain structure of GH13 20, including an N-terminal domain (classified as CBM34), the catalytic module composed of the A- and B- domains, and a C- terminal domain, was found in five of the encoded enzymes (abbreviated Amy1, 89, 92, 98 and 132). These five enzymes degraded cyclomaltodextrins (CDs) and starch, while only three, Amy92 (L. sacchari), Amy98 (A. flavithermus) and Amy132 (environmental DNA), also harboured neopullulanase activity. The L. sacchari enzyme was monomeric, but with CD as the preferred substrate, which is an unusual combination. The sixth enzyme (Amy29 from environmental DNA), was composed of the ABC-domains only. Preferred substrate for Amy29 was pullulan, which was degraded to panose, and the enzyme had no detectable activity on CDs. In addition to its different activity pro. le and domain composition, Amy29 also displayed a different conservation (LPKF) in the fifth conserved region (MPKL) proposed to identify the subfamily. All enzymes had apparent temperature optima in the range 50-65 degrees C, while thermostability varied, and was highest for Amy29 with a half-life of 480 min at 80 degrees C. Calcium dependent activity or stability was monitored in four enzymes, but could not be detected for Amy29 or 98. Tightly bound calcium can, however, not be ruled out, and putative calcium ligands were conserved in Amy98.

Avdelning/ar

Publiceringsår

2008

Språk

Engelska

Sidor

1006-1014

Publikation/Tidskrift/Serie

Biologia

Volym

63

Issue

6

Dokumenttyp

Konferensbidrag

Förlag

Versita

Ämne

  • Industrial Biotechnology

Nyckelord

  • starch
  • environmental DNA
  • GH13
  • cyclomaltodextrinase
  • calcium
  • neopullulanase
  • maltogenic amylase

Conference name

5th International Symposiium Biology and Taxonomy of Green Algae

Conference date

2007-06-25 - 2007-06-29

Conference place

Smolenice, Slovakia

Status

Published

ISBN/ISSN/Övrigt

  • ISSN: 0006-3088