We developed a specific antibody to the catalytic subunit (C-subunit) of cyclic AMP-dependent protein kinase and used it to localize C-subunit in cultured cells. C-subunit antigen was purified from bovine cardiac muscle and cross-linked to hemocyanin with glutaraldehyde. Immunized goat serum showed a low titer of antibody after boosting; it was enriched 100-fold by affinity chromatography on ca...

Although phosphorylation of Thr-197 in the activation loop of the catalytic subunit of cAMP-dependent protein kinase (PKA) is an essential step for its proper biological function, the kinase responsible for this reaction in vivo has remained elusive. Using nonphosphorylated recombinant catalytic subunit as a substrate, we have shown that the phosphoinositide-dependent protein kinase, PDK1, expr...

Protein substrates for an endogenous CA++/calmodulin-dependent protein kinase were characterized in the Aplysia nervous system. Ethylene glycol bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid-washed membrane fractions from Aplysia ganglia contain an endogenous Ca++/calmodulin-dependent protein kinase which phosphorylates a number of membrane proteins. Such washed membrane preparations exh...

We recently compared 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 (Hornbuckle LA, Edgerton DS, Ayala JE, Svitek CA, Neal DW, Cardin S, Cherrington AD, and O'Brien RM. Am J Physiol Endocrinol Metab 281: E713-E725, 2001). In pancreatic-clamped, euglycemic conscious dogs, a 5-h ...

PURPOSE To determine whether the overexpression of the proteasome catalytic beta5 subunit (PSMB5) can induce the expression of the catalytic subunits beta1 and beta2, enhance proteasome activity, and exert a cytoprotective effect in lens epithelial cells. METHODS Cells from the human lens epithelial cell line SRA01/04 (LECs) were stably transfected either with a plasmid expressing the proteas...

Glucose-6-phosphatase (Glu-6-Pase) catalyzes the terminal step of gluconeogenesis, the conversion of glucose 6-phosphate (Glu-6-P) to free glucose. This enzyme activity is thought to be conferred by a complex of proteins residing in the endoplasmic reticulum (ER), including a Glu-6-P translocase that transports Glu-6-P into the lumen of the ER, a phosphohydrolase catalytic subunit residing in t...

Kinetic constants for peptide phosphorylation by the catalytic subunit of the dimorphic fungus Mucor rouxii protein kinase A were determined using 13 peptides derived from the peptide containing the basic consensus sequence RRASVA, plus kemptide, S6 peptide, and protamine. As a whole, although with a greater Km, the order of preference of the peptides by the M. rouxii catalytic subunit was simi...

In the post-genomic era, functional prediction of genes is largely based on sequence similarity searches, but sometimes the homologues bear different roles because of evolutionary adaptations. For instance, the existence of enzyme and non-enzyme homologues poses a difficult case for function prediction and the extent of this phenomenon is just starting to be surveyed. Different evolutionary pat...

Maize phosphoenolpyruvate carboxylase (PEPC) was rapidly and completely inactivated by very low concentrations of trypsin at 37 degrees C. PEP+Mg2+ and several other effectors of PEP carboxylase offered substantial protection against trypsin inactivation. Inactivation resulted from a fairly specific cleavage of 20 kDa peptide from the enzyme subunit. Limited proteolysis under catalytic conditio...