Subcellular localization and kinetic properties of phosphatidylinositol 4,5-bisphosphate phospholipase C and inositol phosphate enzymes from human peripheral blood mononuclear cells.
Peripheral blood mononuclear cells from normal donors exhibited phosphatidylinositol 4,5-bisphosphate phospholipase C (PIP2-PLC), inositol 1,4,5-trisphosphate (IP3) and inositol 1-phosphate (IP)-monophosphatase activities which were mostly recovered in the cytosol fraction. In both cytosol and particulate fractions PIP2-PLC displayed the highest activity at pH 6.2, whereas IP3 and IP-monophosphatases showed the same optimal pH at 7.0. While the PIP2-PLC displayed close apparent Km values in cytosol and particulate fractions, both inositol-monophosphatases were found to show substrate affinities for IP and IP3 characteristic of these two fractions, with an higher affinity in the soluble fraction.
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Laboratorio di Patologia Cellulare, Istituto Cantonale di Patologia, Locarno, Switzerland.
Losa
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GA
D015720:5'-Nucleotidase; D006801:Humans; D007700:Kinetics; D009000:Monocytes / Q000201:enzymology*; D009708:Nucleotidases / Q000097:blood; D010744:Phosphoric Monoester Hydrolases / Q000097:blood*; D012016:Reference Values; D013347:Subcellular Fractions / Q000201:enzymology*; D010738:Type C Phospholipases / Q000097:blood*; D005723:gamma-Glutamyltransferase / Q000097:blood
D005723:gamma-Glutamyltransferase; D009708:Nucleotidases; D010744:Phosphoric Monoester Hydrolases; C022700:sugar-phosphatase; C021822:myo-inositol-1 (or 4)-monophosphatase; D015720:5'-Nucleotidase; D010738:Type C Phospholipases