<p>Mannose-6-phosphate isomerase or phosphomannose isomerase (<db_xref db="EC" dbkey="5.3.1.8"/>) (PMI) is the enzyme that catalyses the interconversion of mannose-6-phosphate and fructose-6-phosphate. In eukaryotes PMI is involved in the synthesis of GDP-mannose, a constituent of N- and O-linked glycans and GPI anchors and in prokaryotes it participates in a variety of pathways, including capsular polysaccharide biosynthesis and D-mannose metabolism. PMI's belong to the cupin superfamily whose functions range from isomerase and epimerase activities involved in the modification of cell wall carbohydrates in bacteria and plants, to non-enzymatic storage proteins in plant seeds, and transcription factors linked to congenital baldness in mammals [<cite idref="PUB00007419"/>]. Three classes of PMI have been defined [<cite idref="PUB00001448"/>].</p><p>This group represents a mannose-6-phosphate isomerase, Firmicutes type, short form.</p>