Galactose mutarotase

Function

Galactose mutarotase (GalM) reversibly converts α-lactose to β-lactose. GalM catalyzes the first step in galactose metabolism^[1].

Structural highlights

From extensive study of mutations in Lactococcus lactis GalM complexes with various sugars it was found that residues H170 and E304 are critical for the active site binding.

Whole active site. Water molecules shown as red spheres.

Na coordination site.

3D structures of galactose mutarotase

Updated on 30-July-2020

1snz – hGalM – human

1so0 - hGalM (mutant) + α-D-galactose
1l7j – LlGalM – Lactococcus lactis
1l7k, 1ns0, 1ns2, 1ns8, 1nsu, 1nsx – LlGalM (mutant) + α-D-galactose
1mmu, 1ns4, 1ns7, 1nsr, 1nss, 1nsv – LlGalM (mutant) + β-D-glucose
1nsz – LlGalM (mutant) + α-D-glucose
1mmx – LlGalM (mutant) + α-L-fuccose
1mmy – LlGalM (mutant) + D-quinovose
1mmz – LlGalM (mutant) + β-L-arabinose
1mn0 – LlGalM (mutant) + D-xylose
1nsm – LlGalM (mutant) + α-D-galactose + β-D-galactose
1lur – GalM – Caenorhabditis elegans
3mwx, 4bze - BsGalM – Bacillus subtilis
4bzf - BsGalM + trehalose
4bzg - BsGalM + maltose
4bzh - BsGalM + trehalose + maltose
3nre – GalM – Escherichia coli

References

1. ↑ Thoden JB, Kim J, Raushel FM, Holden HM. The catalytic mechanism of galactose mutarotase. Protein Sci. 2003 May;12(5):1051-9. PMID:12717027