L-rhamnose mutarotase involved in ulvan degradation (PubMed:31285597). Ulvan is the main polysaccharide component of the Ulvales (green seaweed) cell wall. It is composed of disaccharide building blocks comprising 3-sulfated rhamnose (Rha3S) linked to D-glucuronic acid (GlcA), L-iduronic acid (IduA), or D-xylose (Xyl) (Probable). L-rhamnose mutarotase catalyzes the anomeric conversion of alpha- to beta-L-rhamnose (PubMed:31285597). alpha-L-rhamnose = beta-L-rhamnose Carbohydrate metabolism; L-rhamnose metabolism. Homodimer. Belongs to the rhamnose mutarotase family.