Comparison of protein acetyltransferase action of CRTAase with the prototypes of HAT.

Our laboratory is credited for the discovery of enzymatic acetylation of protein, a phenomenon unknown till we identified an enzyme termed acetoxy drug: protein transacetylase (TAase), catalyzing the transfer of acetyl group from polyphenolic acetates to receptor proteins (RP). Later, TAase was identified as calreticulin (CR), an endoplasmic reticulum luminal protein. CR was termed calreticulin transacetylase (CRTAase).

Solvent effect profiles of absorbance and fluorescence spectra of some indole based chalcones.

The photophysical properties of a series of 3-(1'H-Indol-3'-yl)-1-phenylprop-2-en-1-one and its derivatives (indole chalcones) were studied in different solvents. Solvent effects on the absorption and fluorescence spectra were quantified using Reichardt's and bulk solvent polarity parameters and were complemented by the results of the Kamlet-Taft treatment. The observed excited state dipole moment was found to be larger than the ground state dipole moment of these chalcones.

Protein acyltransferase function of purified calreticulin: the exclusive role of P-domain in mediating protein acylation utilizing acyloxycoumarins and acetyl CoA as the acyl group donors.

The distinct biochemical function of endoplasmic reticulum (ER) protein Calreticulin (CR) catalyzing the transfer of acyl group from acyloxycoumarin to a receptor protein was termed calreticulin transacylase (CRTAase). The present study, unlike the previous reports of others utilizing CR-deficient cells alone, dealt with the recombinant CR domains of Heamonchus contortus (rhCRTAase) in order to examine their CRTAase activity. P-domain of rhCR unlike N- and C-domains was found to be endowed with CRTAase function.

Structure-activity relationship of dihydroxy-4-methylcoumarins as powerful antioxidants: correlation between experimental & theoretical data and synergistic effect.

The chain-breaking antioxidant activities of eight coumarins [7-hydroxy-4-methylcoumarin (1), 5,7-dihydroxy-4-methylcoumarin (2), 6,7-dihydroxy-4-methylcoumarin (3), 6,7-dihydroxycoumarin (4), 7,8-dihydroxy-4-methylcoumarin (5), ethyl 2-(7,8-dihydroxy-4-methylcoumar-3-yl)-acetate (6), 7,8-diacetoxy-4-methylcoumarin (7) and ethyl 2-(7,8-diacetoxy-4-methylcoumar-3-yl)-acetate (8)] during bulk lipid autoxidation at 37 degrees C and 80 degrees C in concentrations of 0.01-1.0 mM and their radical scavenging activities at 25 degrees C using TLC-DPPH test have been studied and compared.

Calreticulin transacylase: genesis, mechanism of action and biological applications.

Our earlier investigations have identified a unique enzyme in the endoplasmic reticulum (ER) termed Acetoxy Drug: Protein Transacetylase (TAase) catalyzing the transfer of acetyl group from polyphenolic acetates (PA) to certain receptor proteins (RP). An elegant assay procedure for TAase was developed based on the inhibition of glutathione S-transferase (GST) due to acetylation by a model acetoxycoumarin, 7, 8-Diacetoxy-4-methylcoumarin (DAMC). TAase purified from various mammalian tissue microsomes to homogeneity exhibited a molecular weight (M.

Protein acyltransferase function of purified calreticulin. Part 1: characterization of propionylation of protein utilizing propoxycoumarin as the propionyl group donor.

We have earlier reported that an endoplasmic reticulum luminal protein calreticulin (CR) mediated the acetylation of certain receptor proteins such as glutathione S-transferase (GST) by polyphenolic acetates, leading to irreversible inhibition. This function of calreticulin was termed calreticulin transacetylase. In this communication, we have demonstrated for the first time the ability of the purified recombinant calreticulin of a parasitic nematode Haemonchus contortus to transfer propionyl group from 7,8-Dipropoxy-4-methylcoumarin (DPMC) to recombinant Schistosoma japonicum glutathione S-transferase (rGST).

Moonlighting protein in Starkeyomyces koorchalomoides: characterization of dihydrolipoamide dehydrogenase as a protein acetyltransferase utilizing acetoxycoumarin as the acetyl group donor.

In this report we have identified for the first time a transacetylase (TAase) in a mesophilic fungi Starkeyomyces koorchalomoides catalyzing the transfer of acetyl group from polyphenolic acetate (PA) to a receptor protein glutathione S-transferase (GST). An elegant assay procedure was established for TAase based on its ability to mediate inhibition of GST by 7,8-diacetoxy-4-methylcoumarin (DAMC), a model PA. Utilizing this assay procedure, S.

Autoacetylation of purified calreticulin transacetylase utilizing acetoxycoumarin as the acetyl group donor.

Our earlier reports documented that calreticulin, a multifunctional Ca2+-binding protein in endoplasmic reticulum lumen, possessed protein acetyltransferase function termed Calreticulin Transacetylase (CRTAase). The autoacetylation of purified human placental CRTAase concomitant with the acetylation of receptor proteins by a model acetoxycoumarin, 7,8-Diacetoxy-4-methylcoumarin, was observed. Here, we have examined the autoacetylation property of CRTAase by immunoblotting and mass spectrometry.

Calreticulin transacetylase mediates the acetylation of nitric oxide synthase by polyphenolic acetate.

Our earlier investigations identified acetoxy drug: protein transacetylase (TAase), a unique enzyme in the endoplasmic reticulum (ER) catalyzing the transfer of acetyl groups from polyphenolic acetates (PA) to certain functional proteins. Recently we have established the identity of TAase with ER protein calreticulin (CR) and subsequently transacetylase function of CR was termed calreticulin transacetylase (CRTAase). CRTAase was purified and characterized from human placenta.

Solubilization of 5-methoxy tryptamine molecular probes in CTAB and SDS micelles: a cmc and binding constant study.

To understand the change in environmental conditions when a probe is incorporated in micelles, an absorption and fluorescence spectral study on the solubilization behaviour of 5-methoxy tryptamine (5-MT) and N,N-dimethyl-5-methoxy tryptamine (5-NMT) has been made in CTAB and SDS for their neutral and cationic forms. The blue shift in emission wavelength is accompanied by increase in intensity with increasing surfactant concentration for almost all the cases except for the cationic probe in CTAB surfactant. This exceptional behaviour can be attributed to the quenching of emission intensity caused by Br(-) ions.

Characterization of protein transacetylase from human placenta as a signaling molecule calreticulin using polyphenolic peracetates as the acetyl group donors.

We have earlier shown that a unique membrane-bound enzyme mediates the transfer of acetyl group(s) from polyphenolic peracetates (PA) to functional proteins, which was termed acetoxy drug: protein transacetylase (TAase) because it acted upon several classes of PA. Here, we report the purification of TAase from human placental microsomes to homogeneity with molecular mass of 60 kDa, exhibiting varying degrees of specificity to several classes of PA confirming the structure-activity relationship for the microsome-bound TAase. The TAase catalyzed protein acetylation by a model acetoxy drug, 7,8-diacetoxy-4-methyl coumarin (DAMC) was established by the demonstration of immunoreactivity of the acetylated target protein with anti-acetyl lysine antibody.

Effect of CTAB and SDS micelles on the excited state equilibria of some indole probes.

The absorption and fluorescence spectral characteristics of some biologically active indoles have been studied as a function of acidity and basicity (H_/pH/H(o)) in cationic (cetyltrimethylammonium bromide, CTAB), anionic (sodium dodecylsulphate, SDS) and aqueous phases at a given surfactant concentration. The prototropic equilibrium reactions of these probes have been studied in aqueous and micellar phases and apparent excited state acidity constant (pK(a)(*)) values are calculated. The probes show formation of different species on changing pH.

Specificities of acetoxy derivatives of coumarins, biscoumarins, chromones, flavones, isoflavones and xanthones for acetoxy drug: protein transacetylase.

The earlier work carried out in our laboratory led to the identification of a novel rat liver microsomal enzyme termed as acetoxy drug: protein transacetylase (TAase), catalyzing the transfer of acetyl group from polyphenolic acetates (PA) to functional proteins. In this paper, we have reported the comparison of the specificities of acetoxy derivatives of coumarins, biscoumarins, chromones, flavones, isoflavones and xanthones with special reference to the phenyl moiety/bulky group on the pyran ring of PA. The results clearly indicated that compounds having phenyl moieties, when used as the substrates, resulted in a significant reduction of TAase catalyzed activity.

Solvatochromic study of excited state dipole moments of some biologically active indoles and tryptamines.

Absorption and fluorescence spectra of some biologically active indole and tryptamine derivatives have been recorded at room temperature in solvents of different polarities. The interest in the photophysical properties of these molecules arises mainly from their utility in medicinal chemistry as neurotransmitter and hallucination/hallucinic agents. Excited-state dipole moments of these molecules have been estimated from solvent-dependent Stokes shift data using a solvatochromic method based on a microscopic solvent polarity parameter (ETN).

Mechanism of biochemical action of substituted 4-methylcoumarins. Part 11: Comparison of the specificities of acetoxy derivatives of 4-methylcoumarin and 4-phenylcoumarin to acetoxycoumarins: protein transacetylase.

Our earlier observations led to the identification of a microsomal enzyme termed as acetoxy drug: protein transacetylase (TAase) catalyzing the transfer of acetyl groups from acetylated polyphenols to the receptor proteins. TAase was conveniently assayed by the irreversible inhibition of cytosolic glutathione S-transferase (GST) by the model acetoxycoumarin, 7,8-diacetoxy-4-methylcoumarin (1). The specificities of the acetoxy group on the benzenoid ring and position of the pyran carbonyl group of the coumarin with respect to oxygen heteroatom for the catalytic activity of TAase were also reported earlier.

Excited state characteristics of acridine dyes: acriflavine and acridine orange.

The magnitude of the Stokes shift (frequency shifts in absorption and fluorescence spectra) is observed on changing the solvents and further has been used to calculate experimentally the dipole moments (ground state and excited state) of acriflavine and acridine orange dye molecules. Theoretically, dipole moments are calculated using PM 3 Model. The dipole moments of excited states, for both molecules investigated here, are higher than the corresponding values in the ground states.

Influence of solvent and substituent on excited state characteristics of laser grade coumarin dyes.

Absorption and fluorescence emission of 4 and 7 substituted coumarins viz. C 440, C 490, C 485 and C 311 have been studied in various polar and non-polar organic solvents. These coumarin dyes are substituted with alkyl, amine and fluorine groups at 4- and 7-positions.

Mechanism of biochemical action of substituted 4-methylbenzopyran-2-ones. Part 9: comparison of acetoxy 4-methylcoumarins and other polyphenolic acetates reveal the specificity to acetoxy drug: protein transacetylase for pyran carbonyl group in proximity to the oxygen heteroatom.

The evidences for the possible enzymatic transfer of acetyl groups (catalyzed by a transacetylase localized in microsomes) from an acetylated compound (acetoxy-4-methylcoumarins) to enzyme proteins leading to profound modulation of their catalytic activities was cited in our earlier publications in this series. The investigations on the specificity for transacetylase (TA) with respect to the number and positions of acetoxy groups on the benzenoid ring of coumarin molecule revealed that acetoxy groups in proximity to the oxygen heteroatom (at C-7 and C-8 positions) demonstrate a high degree of specificity to TA. These studies were extended to the action of TA on acetates of other polyphenols, such as flavonoids and catechin with a view to establish the importance of pyran carbonyl group for the catalytic activity.