1.What Are the Potential Sites of Protein Arylation by N-Acetyl-p-benzoquinone Imine (NAPQI)?
Leeming MG1, Gamon LF1, Wille U1, Donald WA2, O'Hair RA1. Chem Res Toxicol. 2015 Nov 16;28(11):2224-33. doi: 10.1021/acs.chemrestox.5b00373. Epub 2015 Nov 2.
Acetaminophen (paracetamol, APAP) is a safe and widely used analgesic medication when taken at therapeutic doses. However, APAP can cause potentially fatal hepatotoxicity when taken in overdose or in patients with metabolic irregularities. The production of the electrophilic and putatively toxic compound N-acetyl-p-benzoquinone imine (NAPQI), which cannot be efficiently detoxicated at high doses, is implicated in APAP toxicity. Numerous studies have identified that excess NAPQI can form covalent linkages to the thiol side chains of cysteine residues in proteins; however, the reactivity of NAPQI toward other amino acid side chains is largely unexplored. Here, we report a survey of the reactivity of NAPQI toward 11 N-acetyl amino acid methyl esters and four peptides. (1)H NMR analysis reveals that NAPQI forms covalent bonds to the side-chain functional groups of cysteine, methionine, tyrosine, and tryptophan residues. Analogous reaction products were observed when NAPQI was reacted with synthetic model peptides GAIL-X-GAILR for X = Cys, Met, Tyr, and Trp.
2.Involvement of the monoamine system in antidepressant-like properties of 4-(1-phenyl-1h-pyrazol-4-ylmethyl)-piperazine-1-carboxylic acid ethyl ester.
Galdino PM1, de Oliveira DR2, Florentino IF2, Fajemiroye JO2, Valadares MC3, de Moura SS3, da Rocha FF4, de Lima TC5, Costa EA6, Menegatti R7. Life Sci. 2015 Dec 15;143:187-93. doi: 10.1016/j.lfs.2015.11.009. Epub 2015 Nov 10.
AIMS: Piperazinic derivatives have therapeutic potential by acting as analgesic, antidepressant-like, anticonvulsant and antipsychotic in preclinical studies. In order to develop new drugs to treat mental disorders, we designed and synthesized the 4-(1-phenyl-1H-pyrazol-4-ylmethyl)-piperazine-1-carboxylic acid ethyl ester (PPMP), a new piperazine derivative with putative activities on central nervous system that seems to involve serotonergic system.
3.Changes in Carboxy Methylation and Tyrosine Phosphorylation of Protein Phosphatase PP2A Are Associated with Epididymal Sperm Maturation and Motility.
Dudiki T1, Kadunganattil S1, Ferrara JK1, Kline DW1, Vijayaraghavan S1. PLoS One. 2015 Nov 16;10(11):e0141961. doi: 10.1371/journal.pone.0141961. eCollection 2015.
Mammalian sperm contain the serine/threonine phosphatases PP1γ2 and PP2A. The role of sperm PP1γ2 is relatively well studied. Here we confirm the presence of PP2A in sperm and show that it undergoes marked changes in methylation (leucine 309), tyrosine phosphorylation (tyrosine 307) and catalytic activity during epididymal sperm maturation. Spermatozoa isolated from proximal caput, distal caput and caudal regions of the epididymis contain equal immuno-reactive amounts of PP2A. Using demethyl sensitive antibodies we show that PP2A is methylated at its carboxy terminus in sperm from the distal caput and caudal regions but not in sperm from the proximal caput region of the epididymis. The methylation status of PP2A was confirmed by isolation of PP2A with microcystin agarose followed by alkali treatment, which causes hydrolysis of protein carboxy methyl esters. Tyrosine phosphorylation of sperm PP2A varied inversely with methylation. That is, PP2A was tyrosine phosphorylated when it was demethylated but not when methylated.
4.Rhodotorula glutinis Phenylalanine/Tyrosine Ammonia Lyase Enzyme Catalyzed Synthesis of the Methyl Ester of para-Hydroxycinnamic Acid and its Potential Antibacterial Activity.
MacDonald MC1, Arivalagan P2, Barre DE3, MacInnis JA1, D'Cunha GB1. Front Microbiol. 2016 Mar 8;7:281. doi: 10.3389/fmicb.2016.00281. eCollection 2016.
Biotransformation of L-tyrosine methyl ester (L-TM) to the methyl ester of para- hydroxycinnamic acid (p-HCAM) using Rhodotorula glutinis yeast phenylalanine/tyrosine ammonia lyase (PTAL; EC 22.214.171.124) enzyme was successfully demonstrated for the first time; progress of the reaction was followed by spectrophotometric determination at 315 nm. The following conditions were optimized for maximal formation of p-HCAM: pH (8.5), temperature (37°C), speed of agitation (50 rpm), enzyme concentration (0.080 μM), and substrate concentration (0.50 mM). Under these conditions, the yield of the reaction was ∼15% in 1 h incubation period and ∼63% after an overnight (∼18 h) incubation period. The product (p-HCAM) of the reaction of PTAL with L-TM was confirmed using Nuclear Magnetic Resonance spectroscopy (NMR). Fourier Transform Infra-Red spectroscopy (FTIR) was carried out to rule out potential hydrolysis of p-HCAM during overnight incubation. Potential antibacterial activity of p-HCAM was tested against several strains of Gram-positive and Gram-negative bacteria.