Genetic Evidence for a Defective Xylan Degradation Pathway in
            <i>Lactococcus lactis</i>

Erlandson, Karn; Delamarre, Soazig C.; Batt, Carl A.

doi:10.1128/aem.67.4.1445-1452.2001

Cited by 28 publications

(21 citation statements)

References 36 publications

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“…Galactose mutarotase activity has subsequently been observed in a wide range of organisms, including bacteria (3)(4)(5), plants (6,7), fungi (8), and mammals (9)(10)(11) and is present in the cytoplasm of most of these cells. An intriguing case is the Saccharomyces cerevisiae Gal10 where mutarotase occurs as a fusion protein to another enzyme of the Leloir pathway, UDP-glucose 4-epimerase (EC 5.1.3.2) (12).…”

mentioning

confidence: 99%

Lack of aldose 1-epimerase in Hypocrea jecorina (anamorph Trichoderma reesei ): A key to cellulase gene expression on lactose

Fekete

Schink

Kubicek

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

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The heterodisaccharide lactose (1,4-O-␤-D-galactopyranosyl-Dglucose) induces cellulase formation in the ascomycete Hypocrea jecorina ‫؍(‬ Trichoderma reesei). Lactose assimilation is slow, and the assimilation of its ␤-D-galactose moiety depends mainly on the operation of a recently described reductive pathway and depends less on the Leloir pathway, which accepts only ␣-D-galactose. We therefore reasoned whether galactomutarotase [aldose 1-epimerase (AEP)] activity might limit lactose assimilation and thus influence cellulase formation. We identified three putative AEP-encoding genes (aep1, aep2, aep3) in H. jecorina, of which two encoded intracellular protein (AEP1 and AEP2) and one encoded an extracellular protein (AEP3). Although all three were transcribed, only the aep3 transcript was detected on lactose. However, no mutarotase activity was detected in the mycelia, their cell walls, or the extracellular medium during growth on lactose. Therefore, the effect of galactomutarotase activity on lactose assimilation was studied with H. jecorina strains expressing the C-terminal galactose mutarotase part of the Saccharomyces cerevisiae Gal10. These strains showed increased growth on lactose in a gene copy numberdependent manner, although their formation of extracellular ␤-galactosidase activity and transcription of the genes encoding the first steps in the Leloir and the reductive pathway was similar to the parental strain QM9414. Cellulase gene transcription on lactose dramatically decreased in these strains, but remained unaffected during growth on cellulose. Our data show that cellulase induction in H. jecorina by lactose requires the ␤-anomer of D-galactose and reveal the lack of mutarotase activity during growth on lactose as an important key for cellulase formation on this sugar. mutarotase ͉ Leloir pathway ͉ reductive D-galactose catabolism

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confidence: 99%

Lack of aldose 1-epimerase in Hypocrea jecorina (anamorph Trichoderma reesei ): A key to cellulase gene expression on lactose

Fekete

Schink

Kubicek

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

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“…While mutarotase activity was first reported in Escherichia coli in 1965 (2), until recently it was commonly believed that intracellular mutarotation of ␤-D-galactose occurred spontaneously and that this enzyme was not part of the Leloir pathway (1). Since 1986, however, genes encoding enzymes with mutarotase activities have been identified in Acinetobacter calcoaceticus (3), Streptococcus thermophilus (4), Lactobacillus helveticus (5), Haemophilus influenzae (6), E. coli (1) and Lactococcus lactis (7), for example. A survey of the SWISS-PROT data bank reveals ϳ45 amino acid sequences that probably code for mutarotases.…”

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confidence: 99%

“…Here we describe the cloning, expression, purification, and high resolution x-ray crystallographic analysis of galactose mutarotase from L. lactis, both in its apo form to 1.9-Å resolution and complexed with ␣,␤-D-galactose to 1.95-Å resolution. This enzyme was selected for study in part because it is believed to play a key role in linking xylan degradation to xylose metabolism (7). Indeed, xylan degradation represents one-third of all renewable carbon (10).…”

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confidence: 99%

High Resolution X-ray Structure of Galactose Mutarotase from Lactococcus lactis

Thoden

Holden

2002

Journal of Biological Chemistry

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Galactose mutarotase plays a key role in normal galactose metabolism by catalyzing the interconversion of ␤-D-galactose and ␣-D-galactose. Here we describe the three-dimensional architecture of galactose mutarotase from Lactococcus lactis determined to 1.9-Å resolution. Each subunit of the dimeric enzyme displays a distinctive ␤-sandwich motif. This tertiary structural element was first identified in ␤-galactosidase and subsequently observed in copper amine oxidase, hyaluronate lyase, chondroitinase, and maltose phosphorylase.

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“…zymes with mutarotase activities have now been identified in Acinetobacter calcoaceticus (10), Streptococcus thermophilus (11), Lactobacillus helveticus (12), Haemophilus influenzae (13), and Lactococcus lactis (14), among others. A possible catalytic mechanism for galactose mutarotase, first suggested by Hucho and Wallenfels (15) and outlined in Scheme 1, involves the abstraction of a proton from the C-1 hydroxyl group of the sugar by an enzymatic base and donation of a proton to the C-5 oxygen by a side chain acidic group thus resulting in ring cleavage.…”

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confidence: 99%

Structural and Kinetic Studies of Sugar Binding to Galactose Mutarotase from Lactococcus lactis

Thoden¹,

Kim²,

Raushel³

et al. 2002

Journal of Biological Chemistry

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Galactose mutarotase catalyzes the conversion of ␤-Dgalactose to ␣-D-galactose in the Leloir pathway for galactose metabolism. The high resolution x-ray structure of the dimeric enzyme from Lactococcus lactis was recently solved and shown to be topologically similar to the 18-stranded, anti-parallel ␤-motif observed for domain 5 of ␤-galactosidase. In addition to determining the overall molecular fold of galactose mutarotase, this initial investigation also provided a detailed description of the electrostatic interactions between the enzyme and its physiologically relevant substrate, galactose. Specifically, the side chains of His-96 and His-170 were shown to be located within hydrogen bonding distance to the C-5 oxygen of the substrate, while the carboxylate of

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Genetic Evidence for a Defective Xylan Degradation Pathway in Lactococcus lactis

Cited by 28 publications

References 36 publications

Lack of aldose 1-epimerase in Hypocrea jecorina (anamorph Trichoderma reesei ): A key to cellulase gene expression on lactose

Lack of aldose 1-epimerase in Hypocrea jecorina (anamorph Trichoderma reesei ): A key to cellulase gene expression on lactose

High Resolution X-ray Structure of Galactose Mutarotase from Lactococcus lactis

Structural and Kinetic Studies of Sugar Binding to Galactose Mutarotase from Lactococcus lactis

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