Partial Proteolysis of Human L-Type Phosphofructokinase

Abstract

L (liver) type phosphofructokinase subunits purified from human leukocytes are slightly lighter than L subunits from liver and red blood cells. A mild treatment of red blood cell L4 enzyme with subtilisin converts its subunits into forms of similar molecular weight to leukocyte enzyme. From a kinetical point of view, subtilisin-treated L(4) phosphofructokinase and leukocyte enzymes are characterized by a decrease of the allosteric properties as compared to non-treated red cell L(4) phosphofructokinase.

Nature of the subunits of the 6-phosphofructo-1-kinase isoenzymes from rat tissues

“…Although the lower-Mr forms of the C-type subunit were previously unknown, this is not the first report of the detection of altered L-type subunits. It has been reported that the Mr of the L-type subunit from human leucocytes was decreased by 2000 compared with the same subunit from human liver or red blood cells, which had an apparent Mr of 74000-75000 (LaGrange et al, 1981). Also, comparable Mr losses have been obtained after limited proteolysis in vitro of PFK subunits from rabbit skeletal muscle and yeast (Taucher et al, 1975;Kemp & Foe, 1983).…”

Induction of glycolytic enzyme synthesis in proliferating fibroblasts. Study of phosphofructokinase, glucose phosphate isomerase and pyruvate kinase

“…This procedure enables the co-purification of F and L enzymes, which are eluted in the same conditions (Kahn et al, 1980a,b;Lagrange et al, 1981).…”

“…Human phosphofructokinase exists under different forms corresponding to a tetrameric combination of three types of subunits, M, L and F (Cottreau et al, 1979;Kahn et al, 1979Kahn et al, , 1980b fibroblasts, the F subunits (Mr 80000) are predominant; they coexist (Kahn et al, 1979;Weil et al, 1980;Lagrange et al, 1981) with less abundant L subunits (Mr 76 000). The M-type subunits appear to be very rare in these cells (Kahn et al, 1979;Weil et al, 1980;Lagrange et al, 1981). F-type phosphofructokinase is kinetically characterized by poor regulatory properties as compared with M-and L-type enzymes (Meienhofer et al, 1980).…”

“…For further details see the text. L. The L subunits from the platelet phosphofructokinase hybrids are partially proteolysed (Lagrange et al, 1981), which explains their lower Mr than that of the fibroblast L-subunits. The band of Mr approx.…”