Expression and regulation of 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase isozymes in white adipose tissue

The aim of this work was to identify the 6-phosphofructo-2-kinase/fructose- 2,6-bisphosphatase (PFK-2/FBPase-2) isozyme(s) present in white adipose tis sue. Ion-exchange chromatography of PFK-2 from mt epididymal fat pads yield ed an elution pattern compatible with the presence of both the L (liver) an d M (muscle) isozymes. This was consistent with a study of the phosphorylat ion of the purified adipose tissue enzyme by cAMP-dependent protein kinase, by specific labelling of the preparation with [2-P-32]fructose 2,6-bisphos phate and by reaction with antibodies. Characterization of the PFK-2/FBPase -2 mRNAs showed that mature adipocytes express the mRNA that codes for the L isozyme and the two mRNAs that code for the M isozyme. Preadipocytes expr essed mRNA that codes for the M isozyme. Incubation of rat epididymal fat p ads with adrenaline stimulated glycolysis but decreased fructose 2,6-bispho sphate concentrations without significant inactivation of PFK-2. These resu lts support previous findings showing that fructose 2,6-bisphosphate is not involved in the adrenaline-induced stimulation of glycolysis in white adip ose tissue.