GTP cyclohydrolase I (GCH) is the rate-limiting enzyme for the synthesis of tetrahydrobiopterin and its activity is important in the regulation of monoamine neurotransmitters such as dopamine, norepinephrine and serotonin. We have studied the action of divalent cations on the enzyme activity of purified recombinant human GCH expressed in Escherichia coli. First, we showed that the enzyme activity is dependent on the concentration of Mg-free GTP. Inhibition of the enzyme activity by Mg2+, as well as by Mn2+, Co2+ or Zn2+, was due to the reduction of the availability of metal-free GTP substrate for the enzyme, when a divalent cation was present at a relatively high concentration with respect to GTP. We next examined the requirement of Zn2+ for enzyme activity by the use of a protein refolding assay, because the recombinant enzyme contained approximately one zinc atom per subunit of the decameric protein. Only when Zn2+ was present was the activity of the denatured enzyme effectively recovered by incubation with a chaperone protein. These are the first data demonstrating that GCH recognizes Mg-free GTP and requires Zn2+ for its catalytic activity. We suggest that the cellular concentration of divalent cations can modulate GCH activity, and thus tetrahydrobiopterin biosynthesis as well.
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Sci Rep
January 2025
Laboratory of Human Physiology and Pathology, Faculty of Pharmaceutical Sciences, Teikyo University, Tokyo, Japan.
In most patients with type 1 xanthinuria caused by mutations in the xanthine dehydrogenase gene (XDH), no clinical complications, except for urinary stones, are observed. In contrast, all Xdh(- / -) mice die due to renal failure before reaching adulthood at 8 weeks of age. Hypoxanthine or xanthine levels become excessive and thus toxic in Xdh(- / -) mice because enhancing the activity of hypoxanthine phosphoribosyl transferase (HPRT), which is an enzyme that uses hypoxanthine as a substrate, slightly increases the life span of these mice.
View Article and Find Full Text PDFInt J Biol Macromol
January 2025
College of Food Science and Engineering, Ocean University of China, Qingdao 266404, China. Electronic address:
Enzymatic hydrolysis approach is commonly employed for preparation of active peptides, while the limited purity and yield of produced peptides hinder further development of action mechanisms. This study presents the biotechnological approach for the efficient production of recombinant angiotensin converting enzyme (ACE) inhibitory peptide LYPVK and investigates its potential antihypertensive action mechanism. DNA encoding sequence of recombinant peptide was designed to form in tandem, which was expressed in Escherichia coli BL21 (DE3).
View Article and Find Full Text PDFInt J Biol Macromol
January 2025
College of Ocean Food and Biological Engineering, Jimei University, Xiamen 361021, China. Electronic address:
Hemoglobin, composed of α- and β-chains, is essential for oxygen transport and is key in diagnosing and treating gastrointestinal and blood disorders. It also aids in detecting blood contamination and estimating transfusion volumes. Immunological methods, based on antigen-antibody interactions, are distinguished by their high sensitivity and accuracy.
View Article and Find Full Text PDFInt J Biol Macromol
January 2025
School of Food Science and Technology, Shihezi University, Shihezi, Xinjiang 832003, China; Key Laboratory of Characteristics Agricultural Product Processing and Quality Control (Co-construction by Ministry and Province), Ministry of Agriculture and Rural Affairs, Shihezi University, Shihezi, Xinjiang 832000, China; Key Laboratory for Food Nutrition and Safety Control of Xinjiang Production and Construction Corps, Shihezi University, Shihezi, Xinjiang 832000, China. Electronic address:
The limited solubility, rapid metabolism, and poor bioavailability of curcumin restrict its application. In this study, we synthesized chickpea protein isolate (CPI)-citrus pectin (CP) conjugates to prepare an emulsion delivery system that enhances the stability and bioavailability of curcumin. The CPI-CP emulsion achieved a curcumin encapsulation efficiency of 86.
View Article and Find Full Text PDFBioresour Technol
January 2025
State Key Laboratory of Biocatalysis and Enzyme Engineering, Hubei Engineering Research Center for Bio-enzyme Catalysis, Environmental Microbial Technology Center of Hubei Province, School of Life Sciences, Hubei University, Wuhan 430062, PR China. Electronic address:
As an important industrial enzyme, chymosin has been widely used in cheese manufacturing. Fermentation with Kluyveromyces lactis has allowed recombinant chymosin production to fit the growing global demand for cheese consumption; yet improvements can be made to allow for stable and larger-scale production. In this work, various chymosin producing (CP) strains were constructed via targeted chromosomal integration of various copies of a prochymosin expression cassette (PEC) using a CRISPR-Cas9 platform optimized for K.
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