1.Disruption of GABAergic tone in the dorsomedial hypothalamus attenuates responses in a subset of serotonergic neurons in the dorsal raphe nucleus following lactate-induced panic.
Johnson P1, Lowry C, Truitt W, Shekhar A. J Psychopharmacol. 2008 Aug;22(6):642-52. doi: 10.1177/0269881107082900. Epub 2008 Feb 28.
Panic patients are vulnerable to induction of panic attacks by sub-threshold interoceptive stimuli such as intravenous (i.v.) sodium lactate infusions. Facilitation of serotonergic signaling with selective serotonin reuptake inhibitors can suppress anxiety and panic-like responses, but the mechanisms involved are not clearly defined. We investigated the effects of i.v. 0.5 M sodium lactate or saline, in control and panic-prone rats on c-Fos expression in serotonergic neurons within subdivisions of the midbrain/pontine raphe nuclei. Rats were chronically infused with either the GABA synthesis inhibitor l-allylglycine into the dorsomedial hypo thalamus to make them panic-prone, or the enantiomer d-allylglycine (d-AG) in controls. Lactate increased c-Fos expression in serotonergic neurons located in the ventrolateral part of the dorsal raphe nucleus (DRVL) and ventrolateral periaqueductal gray (VLPAG) of control, but not panic-prone, rats. The distribution of lactate-sensitive serotonergic neurons in d-AG-treated rats is virtually identical to previously defined pre-sympathomotor serotonergic neurons with multisynaptic projections to peripheral organs mediating 'fight-or-flight'-related autonomic and motor responses.
2.Metabolism of allylglycine and cis-crotylglycine by Pseudomonas putida (arvilla) mt-2 harboring a TOL plasmid.
Kunz DA, Ribbons DW, Chapman PJ. J Bacteriol. 1981 Oct;148(1):72-82.
Spontaneous mutants which acquired the ability to utilize d-allylglycine (d-2-amino-4-pentenoic acid) and dl-cis-crotylglycine (dl-2-amino-cis-4-hexenoic acid) but not l-allylglycine or dl-trans-crotylglycine could be readily isolated from Pseudomonas putida mt-2 (PaM1). Derivative strains of PaM1 putatively cured of the TOL (pWWO) plasmid were incapable of forming mutants able to utilize the amino acids for growth; however, this ability could be regained by conjugative transfer of the TOL (pWWO) plasmid from a wild-type strain of mt-2 or of the TOL (pDK1) plasmid from a related strain of P. putida (HS1), into cured recipients. dl-Allylglycine-grown cells of one spontaneous mutant (PaM1000) extensively oxidized dl-allylglycine and dl-cis-crotylglycine, whereas only a limited oxidation was observed toward l-allylglycine and dl-trans-crotylglycine. Cell extracts prepared from PaM1000 cells contained high levels of 2-keto-4-hydroxyvalerate aldolase and 2-keto-4-pentenoic acid hydratase, the latter enzyme showing higher activity toward 2-keto-cis-4-hexenoic acid than toward the trans isomer.
3.Synthesis, absolute configuration and activity at N-methyl-D-aspartic acid (NMDA) receptor of the four D-2-amino-4,5-methano-adipate diastereoisomers.
Pellicciari R1, Natalini B, Marinozzi M, Sadeghpour BM, Cordi AA, Lanthorn TH, Hood WF, Monahan JB. Farmaco. 1991 Nov;46(11):1243-64.
The four D-2-amino-4,5-methano-adipates 26, 27, 32, 33 were synthesized and their biological activity at the N-methyl-D-aspartate (NMDA) receptor was assessed. The synthesis involved as a key step a rhodium acetate dimer catalyzed addition of ethyl diazoacetate to the protected D-allylglycine (17). In vitro receptor binding using L-[3H]glutamate as the radioligand provided affinity data, while modulation of [3H]TCP binding was used as a functional assay. The analogues were also evaluated in [3H]kainate and [3H]AMPA binding to assess selectivity over non-NMDA glutamate receptors. Three of the four diastereoisomer, D-CAA B (27), C (32) and D (33) were shown to have agonist properties at the NMDA-site, while the fourth, (2R,4R,5R) D-CAA A (26) was characterized as an NMDA-site atypic antagonist.
4.An improved racemase/acylase biotransformation for the preparation of enantiomerically pure amino acids.
Baxter S1, Royer S, Grogan G, Brown F, Holt-Tiffin KE, Taylor IN, Fotheringham IG, Campopiano DJ. J Am Chem Soc. 2012 Nov 28;134(47):19310-3. doi: 10.1021/ja305438y. Epub 2012 Nov 15.
Using directed evolution, a variant N-acetyl amino acid racemase (NAAAR G291D/F323Y) has been developed with up to 6-fold higher activity than the wild-type on a range of N-acetylated amino acids. The variant has been coupled with an enantiospecific acylase to give a preparative scale dynamic kinetic resolution which allows 98% conversion of N-acetyl-DL-allylglycine into D-allylglycine in 18 h at high substrate concentrations (50 g L(-1)). This is the first example of NAAAR operating under conditions which would allow it to be successfully used on an industrial scale for the production of enantiomerically pure α-amino acids. X-ray crystal analysis of the improved NAAAR variant allowed a comparison with the wild-type enzyme. We postulate that a network of novel interactions that result from the introduction of the two side chains is the source of improved catalytic performance.
