PDE6 (type 6 phosphodiesterase) from rod outer segments consists of two types of catalytic subunits, alpha and beta; two inhibitory gamma subunits; and one or more delta subunits found only on the soluble form of the enzyme. About 70% of the phosphodiesterase activity found in rod outer segments is membrane-bound, and is thought to be anchored to the membrane through C-terminal prenyl groups. T...

Human CPN (carboxypeptidase N) is a tetrameric plasma enzyme containing two glycosylated 83 kDa non-catalytic/regulatory subunits that carry and protect two active catalytic subunits. Because CPN can regulate the level of plasminogen binding to cell surface proteins, we investigated how plasmin cleaves CPN and the consequences. The products of hydrolysis were analysed by activity assays, Wester...

Two mammalian genes for the Ca(2+)-binding regulatory subunit of the calmodulin-dependent protein phosphatase (calcineurin) were identified recently, suggesting unique associations with tissue-specific catalytic subunits. The murine brain (beta 1) and testis (beta 2) isoforms of the regulatory subunit were expressed with poly-histidine carboxyl termini and purified by Ni(2+)-chelate chromatogra...

Protein kinase A (PKA) holoenzyme is one of the major receptors for cyclic adenosine monophosphate (cAMP), where an extracellular stimulus is translated into a signaling response. We report here the structure of a complex between the PKA catalytic subunit and a mutant RI regulatory subunit, RIalpha(91-379:R333K), containing both cAMP-binding domains. Upon binding to the catalytic subunit, RI un...

The mechanism of inactivation of rabbit liver phosphorylase phosphatase by glutathione disulfide (GSSG) was investigated. The catalytic subunit of phosphorylase phosphatase was inactivated by GSSG and other disulfides. Inactivation by GSSG was a concentration-dependent process and resulted in the formation of an inactive, stable enzyme species. The inactivated enzyme could be reactivated by add...

Analysis of cyclic AMP-dependent protein kinase catalytic (C) and regulatory (R) subunits in normal human melanocytes and malignant melanomas demonstrated molar excess of regulatory over catalytic subunit in both cell types. Overall, greater catalytic activity, as a measure of C subunit, and cyclic AMP binding activity, as a measure of R subunit, were detected in metastatic compared to primary ...

The catalytic subunit of cAMP-dependent protein kinase expressed in Escherichia coli is a phosphoprotein. By in vivo labeling with [32Pi]orthophosphate, the sites of phosphorylation were identified as Ser-10, Ser-139, Thr-197, and Ser-338. Two of these sites, Thr-197 and Ser-338, are found in the mammalian enzyme (Shoji, S., Titani, K., Demaille, J. G., and Fischer, E. H. (1979) J. Biol. Chem. ...

Two hybrid versions of Escherichia coli aspartate transcarbamoylase were studied to determine the influence of domain closure on the homotropic and heterotropic properties of the enzyme. Each hybrid holoenzyme had one wild-type and one inactive catalytic subunit. In the first case the inactive catalytic subunit had Arg-54 replaced by alanine. The holoenzyme with this mutation in all six catalyt...

5'-Methylthioadenosine/S-adenosylhomocysteine nucleosidases (MTANs) are bacterial enzymes that catalyze hydrolysis of the N-ribosidic bonds of 5'-methylthioadenosine (MTA) and S-adenosylhomocysteine (SAH) to form adenine and 5-thioribosyl groups. MTANs are involved in AI-1 and AI-2 bacterial quorum sensing and the unusual futalosine-based menaquinone synthetic pathway in Streptomyces, Helicobac...

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 an...