Antioxidant activity of N-acetyl-glucosamine based thiazolidine derivative

N-acetyl-glucosamine, the monomer of chitin, was cyclo-condensed with L-cysteine to prepare thiazolidine derivative： 2-N-acetyl-glucosamine-thiazolidine-4（R）-carboxylic acid （GlcNAcCys）. The stability of GlcNAcCys was evaluated by high performance liquid chromatography （HPLC） measurement. The results showed that GlcNAcCys was more stable than other TCA derivatives, especially in alkaline condition. The direct in vitro antioxidative properties of GlcNAcCys were investigated by using UV radiation-induced lipid peroxidation （LPO） in mitochondria and nuclei and . OH-induced LPO in red blood cell （RBC） ghosts models. UV radiation caused dose-dependent LPO in both mitochondria and nuclei. This effect was catalyzed by addition of Fe^2 ＋ while prevented by co-incubation with GlcNAcCys. When nuclei and mitochondria was treated with 100μl, 300μl, 500μl of GlcNAcCys and co-incubated at 37℃ for 30min, LPO was decreased to 96%, 72%, 68% in nuclei and 95%, 72%, 68% in mitochondria when compared to the UV radiation group respectively. Hydroxyl radicals （. OH） generated by Fenton reaction induced LPO in RBC ghosts. Pretreatment of RBC ghosts with GlcNAcCys could induce antioxidant RBC ghosts and inhibit concentration-dependent malondialdehyde （MDA） formation in antioxidant RBC ghosts. Its inhibition percent was 14%, 35%, 36%, 42% at 10, 20, 30, 40mg/ml respectively. In a conclusion, the data suggest that GlcNAcCys has antioxidant ability and can significantly inhibit lipid peroxidation in biological samples tested in vitro.

Enzymatic production of N‑acetylneuraminic acid:advances and perspectives

N-Acetyl-d-neuraminic acid(NeuAc),a well-known and well-studied sialic acid,is found in cell surface glycolipids and glycoproteins,where it performs a variety of biological functions.The use of NeuAc as a nutraceutical for infant brain development and as an intermediate for pharmaceutical production demands its production on an industrial scale.Natural extraction,chemical synthesis,enzymatic synthesis,and biosynthesis are the methods used for NeuAc production.Among these methods,enzymatic synthesis using N-acetyl-glucosamine(GlcNAc)2-epimerase(AGE)for epimerization and N-acetyld-neuraminic acid lyase(NAL)for aldol condensation,has been reported to produce NeuAc with high production efciency.In this review,we discuss advances in the two-step enzymatic synthesis of NeuAc using pyruvate and GlcNAc as substrates.The major challenges in producing NeuAc with high yield are highlighted,including multiple parameter-dependent processes,undesirable reversibility,and diminished solubility of AGEs and NALs.Further,diferent strategies applied to overcome the limitations of the two-step enzymatic production are discussed,such as pyruvate concentration and temperature shift during the process to increase conversion yield,use of mathematical and computational simulations for process optimization,enzyme engineering to make enzymes highly efcient,and the use of tags and chaperones to increase enzyme solubility.We suggest future directions and the strategies that can be followed to improve enzymatic synthesis of NeuAc.