Regulation of fructose-2,6-bisphosphate content in mantle tissue of the sea musselMytilus galloprovincialis

6-phosphofructo-2-kinase (PFK-2) from the mantle of the sea musselMytilus galloprovincialis Lmk, collected from the Ría de Arosa (NW Spain) in 1990, was purified 550-fold by extraction and sequential affinity chromatography on Affi-gel Blue and ATP-agarose columns. The enzyme was a dimer with a native molecular weight of 100 kilodaltons (KDa) and a subunitM _r of 53 KDa. PFK-2 activity is dependent on the presence of P_i. At physiological P_i concentrations, the enzyme exhibits hyperbolic kinetics with both ATP and Fru-6-P, withK _m values of 0.62 and 0.37 mM respectively. In vivo, PFK-2 activity is limited by the concentration of Fru-6-P which is low in comparison with theK _m for this substrate. Citrate and PEP inhibited PFK-2 activity.