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Biomedical subjects

S G Ramaswamy

Publications and source records attributed to S G Ramaswamy.

8 recordsLinked to original sources
PubMed1998

Enzymatic hydrolysis of organic cyclic carbonates.

Ethylene carbonate, a cyclic organic carbonate widely used industrially, is toxic when metabolically converted to ethylene glycol. A rat liver enzyme active in catalyzing the ring opening has been purified to electrophoretic homogeneity and found to be active in the hydrolysis of ethylene, vinylene, and propylene carbonates to CO2 and the respective glycols. Neither thiocarbonates nor open chain carbonates served as substrate nor did a variety of esters, lactams, lactones, and related heterocycles. The enzyme was active, however, with imides and appears to be identical to rat liver imidase. The identification was confirmed by copurification of enzyme activities, by similarities in the pattern of inhibition, and by the reactivity with a polyclonal antibody directed against the enzyme purified here.

Amidohydrolases↗
PubMed1992

A rabbit autoantibody specific for the 46-kDa form of 2',3'-cyclic nucleotide 3'-phosphodiesterase.

An autoantibody occurring in the serum of an apparently normal rabbit that immunocytochemically stains myelin sheaths and oligodendrocytes in rat brain was shown to react specifically with the 46-kDa isoform of 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNP) (EC 3.1.4.37) in a number of species. Identification of the shorter isoform of the enzyme (CNP1) as the antigen was achieved by comparing the immunostaining of Western blots by the autoantibody with that of a well-characterized anti-CNP antiserum. The 46-kDa antigen reacting with the autoantibody exhibited the same Mr and pI as the small isoform of CNP on two-dimensional gels and showed a similar enrichment in purified CNS myelin. The autoantibody has very high affinity for CNP1 and is capable of detecting the very low amounts of this enzyme in peripheral nerve, spleen, adrenal gland, pancreas, testis, and intestine. Testing the reactivity of the autoantibody with synthetic peptides by enzyme-linked immunosorbent assay revealed that it reacted with the N-acetylated decapeptide corresponding to the N-terminus of CNP1, but did not react if the peptide was not acetylated or if the acetyl group was replaced with a palmityl group. The lack of reactivity with CNP2, which differs from CNP1 by a 20-amino acid extension at the N-terminus of the protein as a result of alternative splicing, may be due to the absence of the N-acetyl moiety that is part of the epitope and/or blocking of antibody binding to the decapeptide by extension of the polypeptide chain.(ABSTRACT TRUNCATED AT 250 WORDS)

2',3'-Cyclic-Nucleotide Phosphodiesterases↗
PubMed1990

A novel autoantibody from a rabbit preimmune serum that immunostains myelinated nerves of the brain.

Preimmune serum from a rabbit was found to contain antibodies that selectively immunostained myelin in brain sections of the rat. It also reacted with oligodendroglial cells in culture as shown by double labeling with galactocerebroside. On Western blots of two-dimensional electrophoretic gels of rat cortex, this antiserum recognized a 46 kD protein with a basic pI. The presence of this protein within myelin may help identify possible cellular mechanisms of myelination and the autoimmune serum might be useful in structural studies of myelin.

Animals↗
PubMed1987

(2')3',5'-Bisphosphate nucleotidase.

(2')3',5'-Bisphosphate nucleotidase has been prepared in electrophoretically homogeneous form from guinea pig liver. The enzyme catalyzes the hydrolysis of the 2'- or 3'-phosphate from the appropriate nucleoside 2',5'- and 3',5'-bisphosphates and is active with 3'-phosphoadenosine 5'-phosphosulfate and with coenzyme A but not with ATP. The 40,000-dalton protein is a monomer that requires Mg2+ for activity.

Adenosine Triphosphate↗
PubMed1987

Amine N-sulfotransferase.

A highly purified amine N-sulfotransferase has been isolated from guinea pig liver that catalyzes sulfuryl group transfer from 3'-phosphoadenosine 5'-phosphosulfate to one of a large number of either primary or secondary amines forming the appropriate sulfamate and adenosine 3',5'-bisphosphate. Amines as different as aniline, 2-naphthylamine, octylamine, 1,2,3,4-tetrahydroisoquinoline and 1,2,3,4-tetrahydroisoquinoline, desmethylimipramine, and cyclohexylamine serve as acceptors; the product of the last of these substrates is the sugar-substitute cyclamate. Amine N-sulfotransferase activity is dependent on the presence of an unprotonated amino group. The purified enzyme preparation also has O-sulfotransferase activities, suggesting that transfer to oxygen could represent an intrinsic function of the N-sulfotransferase.

Animals↗
PubMed1984

Hydroxyproline 2-epimerase of Pseudomonas. Subunit structure and active site studies.

Hydroxyproline 2-epimerase of Pseudomonas putida was purified to homogeneity by an improved procedure. The native enzyme consists of two probably identical subunits. Alkylation of the active site with labeled reagents resulted in the loss of 80-85% of the activity but the incorporation of only one alkyl group even though the active site contains a Cys residue from each of the two subunits. This result suggests that the enzyme shows half-site reactivity. The labeled enzyme was further subjected to exhaustive alkylation with unlabeled iodoacetate, permitting tryptic hydrolysis and isolation of an active site peptide in 30% yield. The specific radioactivity of the peptide was consistent with the first result, that only 1 mol of alkyl group was initially incorporated into active site. The active site peptide (14 residues) was sequenced and found to possess homology with the clostridial proline racemase.

Alkylation↗