In enzymology, a rhamnulokinase (EC 2.7.1.5) is an enzyme that catalyzes the chemical reaction

ATP + L-rhamnulose ${\displaystyle \rightleftharpoons }$ ADP + L-rhamnulose 1-phosphate

Thus, the two substrates of this enzyme are ATP and L-rhamnulose, whereas its two products are ADP and L-rhamnulose 1-phosphate.

This enzyme belongs to the family of transferases, specifically those transferring phosphorus-containing groups (phosphotransferases) with an alcohol group as acceptor. The systematic name of this enzyme class is ATP:L-rhamnulose 1-phosphotransferase. Other names in common use include RhuK, rhamnulokinase (phosphorylating), L-rhamnulokinase, L-rhamnulose kinase, and rhamnulose kinase. This enzyme participates in pentose and glucuronate interconversions and fructose and mannose metabolism. This enzyme can catalyze the xylulose phosphorilation:^[1]

ATP + L-Xylulose ${\displaystyle \rightleftharpoons }$ ADP + L-Xylulose 1-phosphate

As of late 2007, 4 structures have been solved for this class of enzymes by Grueninger and Schulz with PDB accession codes 2CGJ, 2CGK, 2CGL, and 2UYT.

• Wilson DM, Ajl S (March 1957). "Metabolism of L-rhamnose by Escherichia coli. II. The phosphorylation of L-rhamnulose". Journal of Bacteriology. 73 (3): 415–20. doi:10.1128/JB.73.3.415-420.1957. PMC 289814. PMID 13416205.
• D.Grueninger and G.E.Schulz (2006). Structure and reaction mechanism of L-rhamnulose kinase from Escherichia coli.. J. Mol. Biol., 359, 787-797.
• D.Grueninger and G.E.Schulz (2007). Substrate spectrum of L-rhamnulose kinase related to models derived from two ternary complex structures.. FEBS Lett, 581, 3127-3130.