 The nuclear envelope allows the nucleus to control its contents , and separate them from the rest of the cytoplasm where necessary . This is important for controlling processes on either side of the nuclear membrane . In most cases where a <unk> process needs to be restricted , a key participant is removed to the nucleus , where it interacts with transcription factors to <unk> the production of certain enzymes in the pathway . This regulatory mechanism occurs in the case of glycolysis , a cellular pathway for breaking down glucose to produce energy . <unk> is an enzyme responsible for the first the step of glycolysis , forming glucose @-@ 6 @-@ phosphate from glucose . At high concentrations of <unk> @-@ 6 @-@ phosphate , a molecule made later from glucose @-@ 6 @-@ phosphate , a regulator protein removes <unk> to the nucleus , where it forms a transcriptional <unk> complex with nuclear proteins to reduce the expression of genes involved in glycolysis . 
