it is now well established that the type la of serine/threonine protein phosphatases (pp1α) may be implicated in malignant phenotype. although the pp1α mrna level increased in livers at preneo-plastic stages of hepatocarinogenesis and all of examined rat ascites hepatomas, unexpectedly, dra-matically decreased in some of primary hepatomas. in order to elucidate the low level of pp1α mrna in som...

we have investigated the effect of theophylline on the kinetics of the catalytic subunit of protein kinase and related factors in lung tissue. the results show that the point of highest concentration of the c subunit of protein kinase which is active in casein phosphorylation is at 3h of incubation time, but in the presence of 100 ilg/ inl and 10µg/ml theophylline, this is shifted to i.s and 2....

A specific antiserum against bovine heart catalytic subunit was used for the determination of the catalytic subunit in an enzyme-linked immunosorbent assay. Under the conditions elaborated the assay has a lower detection limit for catalytic subunit of 0.25 pmol/ml. In crude bovine heart extracts the concentration of catalytic subunit was determined by this method to be 0.18 +/- 0.02 mumol/kg we...

The interaction of a protein inhibitor with the catalytic subunit derived from adenosine 3’,5’-monophosphatedependent protein kinase is described. A kinetic analysis of casein phosphorylation in the presence of inhibitor reveals a noncompetitive interaction between the inhibitor and the catalytic subunit substrates, ATP and casein. The inhibitor does not function by destroying ATP nor by acting...

1. The molecular weights of the catalytic and regulatory polypeptide chains of aspartate transcarbamylase were determined to be 33,500 and 17,000, respectively. The results of three empirical methods are in good agreement with those obtained by sedimentation equilibrium in guanidine-hydrochloride or derived from the intrinsic viscosity and the sedimentation coefficient measured in the same solv...

Protein Phosphatase 2A (PP2A) plays an essential role in many aspects of cellular physiology. The PP2A holoenzyme consists of a heterodimeric core enzyme, which comprises a scaffolding subunit and a catalytic subunit, and a variable regulatory subunit. Here we report the crystal structure of the heterotrimeric PP2A holoenzyme involving the regulatory subunit B'/B56/PR61. Surprisingly, the B'/PR...

cAMP-dependent protein kinase mediates a variety of cellular responses in most eukaryotic cells. Many of these responses are cytoplasmic, whereas others appear to require nuclear localization of the catalytic subunit. In order to understand further the molecular basis for subcellular localization of the catalytic subunit, the effect of the heat stable protein kinase inhibitor (PKI) was investig...

The catalytic subunit of adenosine cyclic 3',5'-monophosphate dependent protein kinase from bovine skeletal muscle was rapidly inactivated by o-phthalaldehyde at 25 degrees C (pH 7.3). The reaction followed pseudo-first-order kinetics, and the second-order rate constant was 1.1 X 10(2) M-1 s-1. Absorbance and fluorescence spectroscopic data were consistent with the formation of an isoindole der...

A limited reduction of the disulfide bonds of bovine enterokinase (enteropeptidase, EC 3.4.21.9) was accomplished with 50 mM dithioerythritol, at pH 9.0, and at 4 degrees C. The conditions separated the heavy and light subunits quantitatively with improved reliability when compared to the conditions used previously (Savithri, H. S., and Light, A. (1980) Biochim. Biophys. Res. Commun, 94, 360-36...

The regulation of glucose-6-phosphatase (G-6-Pase) catalytic subunit and glucose 6-phosphate (G-6-P) transporter gene expression by insulin in conscious dogs in vivo and in tissue culture cells in situ were compared. In pancreatic-clamped, euglycemic conscious dogs, a 5-h period of hypoinsulinemia led to a marked increase in hepatic G-6-Pase catalytic subunit mRNA; however, G-6-P transporter mR...