Giardia lamblia arginine deiminase (GlAD), the topic of this paper, belongs to the hydrolase branch of the guanidine-modifying enzyme superfamily, whose members employ Cys-mediated nucleophilic catalysis to promote deimination of l-arginine and its naturally occurring derivatives. G. lamblia is the causative agent in the human disease giardiasis. The results of RNAi/antisense RNA gene-silencing studies reported herein indicate that GlAD is essential for G. lamblia trophozoite survival and thus, a potential target for the development of therapeutic agents for the treatment of giardiasis. The homodimeric recombinant protein was prepared in Escherichia coli for in-depth biochemical characterization. The 2-domain GlAD monomer consists of a N-terminal domain that shares an active site structure (depicted by an insilico model) and kinetic properties (determined by steady-state and transient state kinetic analysis) with its bacterial AD counterparts, and a C-terminal domain of unknown fold and function. GlAD was found to be active over a wide pH range and to accept l-arginine, l-arginine ethyl ester, N(alpha)-benzoyl-l-arginine, and N(omega)-amino-l-arginine as substrates but not agmatine, l-homoarginine, N(alpha)-benzoyl-l-arginine ethyl ester or a variety of arginine-containing peptides. The intermediacy of a Cys424-alkylthiouronium ion covalent enzyme adduct was demonstrated and the rate constants for formation (k(1)=80s(-1)) and hydrolysis (k(2)=35s(-1)) of the intermediate were determined. The comparatively lower value of the steady-state rate constant (k(cat)=2.6s(-1)), suggests that a step following citrulline formation is rate-limiting. Inhibition of GlAD using Cys directed agents was briefly explored. S-Nitroso-l-homocysteine was shown to be an active site directed, irreversible inhibitor whereas N(omega)-cyano-l-arginine did not inhibit GlAD but instead proved to be an active site directed, irreversible inhibitor of the Bacillus cereus AD.
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http://dx.doi.org/10.1016/j.bioorg.2009.06.001 | DOI Listing |
Biochemistry
January 2025
Department of Chemistry, University of California, Berkeley, California 94720, United States.
In many bacteria, the location of the mRNA start codon is determined by a short ribosome binding site sequence that base pairs with the 3'-end of 16S rRNA (rRNA) in the 30S subunit. Many groups have changed these short sequences, termed the Shine-Dalgarno (SD) sequence in the mRNA and the anti-Shine-Dalgarno (ASD) sequence in 16S rRNA, to create "orthogonal" ribosomes to enable the synthesis of orthogonal polymers in the presence of the endogenous translation machinery. However, orthogonal ribosomes are prone to SD-independent translation.
View Article and Find Full Text PDFBiochemistry
January 2025
Department of Chemistry, Texas A&M University, College Station, Texas 77842, United States.
The exterior surface of the human pathogen is coated with a capsular polysaccharide (CPS) that consists of a repeating sequence of 2-5 different sugars that can be modified with various molecular decorations. In the HS:2 serotype from strain NCTC 11168, the repeating unit within the CPS is composed of d-ribose, -acetyl-d-galactosamine, and a d-glucuronic acid that is further amidated with either serinol or ethanolamine. The d-glucuronic acid moiety is also decorated with d-glycero-l-gluco-heptose.
View Article and Find Full Text PDFSmall
January 2025
School of Chemical Engineering and Technology, Xi'an Jiaotong University, Xi'an, 710049, China.
The photocatalytic conversion of CO into products such as CH and CH poses a significant challenge due to the lengthy reaction steps and the high energy barrier involved. In this study, both benzothiadiazole (BTD) and hydroxyl groups (-OH) are introduced into cobalt-based polymerized porphyrinic network (PPN) through a C-C coupling reaction. This modification of orbital energy levels that strengthens the ability of gain electrons and facilitates the charge transfer in PPN.
View Article and Find Full Text PDFACS Nano
January 2025
School of Medicine and Health, Harbin Institute of Technology, Harbin 150080, China.
Modularly organizing active micromachines into high-grade metamachines makes a great leap for operating the microscopic world in a biomimetic way. However, modulating the nonreciprocal interactions among different colloidal motors through chemical reactions to achieve the controllable construction of active colloidal metamachines with specific dynamic properties remains challenging. Here, we report the phototactic active colloidal metamachines constructed by shape-directed dynamic self-assembly of chemically driven peanut-shaped TiO colloidal motors and Janus spherical Pt/SiO colloidal motors.
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January 2025
CSSC Nanjing Lvzhou Environmental Protection Co., Ltd, Nanjing 210039, China.
In this study, the MnFeO@CoS magnetic nanocomposite was prepared by a two-step hydrothermal method and used to catalyze the ozone oxidation degradation of methylene blue. It was characterized by XRD, EDS, SEM, FT-IR, and XPS. The results showed that the introduction of CoS made MnFeO grow uniformly on CoS nanosheets, which effectively prevented the agglomeration of MnFeO.
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