Phosphofructokinase in alveolar type II cells isolated from fetal and adult rat lung

• Published in: Biochimica et biophysica acta Vol. 1002; no. 3; pp. 388 - 394
• Main Authors: Heesbeen, Ellen C., Rijksen, Gert, Batenburg, Joseph J., van Golde, Lambert M.G., Staal, Gerard E.J.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 26.04.1989; Elsevier; North-Holland
• Subjects: 6-Phosphofructokinase; Adenosine Triphosphate - pharmacology; Age Factors; Alveolar type II cell; Analytical, structural and metabolic biochemistry; Animals; Biological and medical sciences; Chromatography, Affinity; Development; Enzyme Activation - drug effects; Enzymes and enzyme inhibitors; Fructose 2,6-bisphosphate; Fructosephosphates - metabolism; Fundamental and applied biological sciences. Psychology; Hexokinase - metabolism; Lung - embryology; Lung - enzymology; Magnesium - pharmacology; Phosphofructokinase-1 - antagonists & inhibitors; Phosphofructokinase-1 - isolation & purification; Phosphopyruvate Hydratase - metabolism; Pulmonary Alveoli - embryology; Pulmonary Alveoli - enzymology; Pyruvate Kinase - metabolism; Rat lung; Rats; Transferases; Development; Alveolar type II cell; Rat lung; Fructose 2,6-bisphosphate; Hepes; 6-Phosphofructokinase; Pyruvate kinase; Rat; Enzyme; Lung; Rodentia; Activation; Subunit; Hexokinase; Vertebrata; Mammalia; Enzymatic activity; Inhibition; Enolase
• ISSN: 0005-2760; 0006-3002; 1879-145X; 1878-2434
• DOI: 10.1016/0005-2760(89)90354-8

The glycolytic enzyme 6-phosphofructokinase (EC 2.7.1.11) was studied in adult and fetal type II pneumocytes which had been isolated from rat lung at different days of development. In addition, the activities of the enzymes hexokinase (EC 2.7.1.1), enolase (EC 4.2.1.11) and pyruvate kinase (EC 2.7.1.40) were assayed. The specific activities of the latter enzymes decrease during perinatal development and reach about adult values shortly after birth. In contrast, 6-phosphofructokinase activity increases slightly until 2 days before birth, and drops sharply afterwards. The 6-phosphofructokinase subunit composition was determined in fetal and adult type II cells. The ratio of the three subunits of 6-phosphofructokinase in type II cells isolated on fetal days 19 and 21 (term is at day 22) and in adult type II cells was identical: the three subunits were present in a ratio of 68:14:18 for types L,M and C, respectively. In addition, we investigated some regulatory properties of 6-phosphofructokinase from alveolar type II cells. 6-Phosphofructokinase from alveolar type II cells is strongly inhibited by increasing MgATP concentrations. This inhibition is reflected by an increase in the S 0.5 for fructose 6-phosphate. Fructose 2,6-bisphosphate stimulates alveolar type II 6-phosphofructokinase. Half-maximal stimulation occurs at 1.6 and 2.0 μM fructose 2,6-bisphosphate for fetal and adult type II cells, respectively. The level of the most potent positive effector of 6-phosphofructokinase, fructose 2,6-bisphosphate, was also determined. The level of the hexose bisphosphate decreases during prenatal development; however, the level in the adult type II cells is considerably lower. The concentration of fructose 2,6-bisphosphate appears to be sufficient to fully activate 6-phosphofructokinase both in fetal and adult type II cells.