Structure-based engineering of heparinase I with improved specific activity for degrading heparin

Identification and characterization of a novel heparinase PCHepII from marine bacterium Puteibacter caeruleilacunae

Heparin (HP) and heparan sulfate (HS) are multifunctional polysaccharides widely used in clinical therapy. Heparinases (Hepases) are enzymes that specifically catalyse HP and HS degradation, and they are valuable tools for studying the structure and function of these polysaccharides and for preparing low molecular weight heparins. In this study, by searching the NCBI database, a novel enzyme named PCHepII was discovered in the genome of the marine bacterium Puteibacter caeruleilacuae. Heterologously expressed PCHepII in Escherichia coli (BL21) has high expression levels and good solubility, active in sodium phosphate buffer (pH 7.0) at 20°C. PCHepII exhibits an enzyme activity of 254 mU/mg towards HP and shows weak degradation capacity for HS. More importantly, PCHepII prefers to catalyse the high-sulfated regions of HP and HS rather than the low-sulfated regions. Although PCHepII functions primarily as an endolytic Hepase, it mainly generates disaccharide products during the degradation of HP substrates over time. Investigations reveal that PCHepII exhibits a preference for catalysing the degradation of small substrates, especially HP tetrasaccharides. The catalytic sites of PCHepII include the residues His199, Tyr254, and His403, which play crucial roles in the catalytic process. The study and characterization of PCHepII can potentially benefit research and applications involving HP/HS, making it a promising enzyme.

Combination of engineering the substrate and Ca2+ binding domains of heparinase I to improve the catalytic activity

Heparinase I (EC 4.2.2.7), is an enzyme that cleaves heparin, showing great potential for eco-friendly production of low molecular weight heparin (LMWH). However, owing to its poor catalytic activity and thermal stability, the industrial application of heparinase I has been severely hindered. To improve the catalytic activity, we proposed to engineer both the substrate and Ca2+ binding domains of heparinase I. Several heparinases I from different organisms were selected for multiple sequence alignment and molecular docking to screen the key residues in the binding domain. Nine single-point mutations were selected to enhance the catalytic activity of heparinase I. Among them, T250D was the most highly active one, whereas mutations around Ca2+ binding domain yielded two active mutants. Mutant D152S/R244K/T250D with significantly increased catalytic activity was obtained by combined mutation. The catalytic efficiency of the mutant was 118,875.8 min-1·µM-1, which was improved 5.26 times. Molecular modeling revealed that the improved activity and stability of the mutants were probably attributed to the formation of new hydrogen bonds. The highly active mutant had great potential applications in industry and the strategy could be used to improve the performance of other enzymes.

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: An update for 2019-2020

This review is the tenth update of the original article published in 1999 on the application of matrix-assisted laser desorption/ionization (MALDI) mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings coverage of the literature to the end of 2020. Also included are papers that describe methods appropriate to analysis by MALDI, such as sample preparation techniques, even though the ionization method is not MALDI. The review is basically divided into three sections: (1) general aspects such as theory of the MALDI process, matrices, derivatization, MALDI imaging, fragmentation, quantification and the use of arrays. (2) Applications to various structural types such as oligo- and polysaccharides, glycoproteins, glycolipids, glycosides and biopharmaceuticals, and (3) other areas such as medicine, industrial processes and glycan synthesis where MALDI is extensively used. Much of the material relating to applications is presented in tabular form. The reported work shows increasing use of incorporation of new techniques such as ion mobility and the enormous impact that MALDI imaging is having. MALDI, although invented nearly 40 years ago is still an ideal technique for carbohydrate analysis and advancements in the technique and range of applications show little sign of diminishing.

Not Just Anticoagulation—New and Old Applications of Heparin

In recent decades, heparin, as the most important anticoagulant drug, has been widely used in clinical settings to prevent and treat thrombosis in a variety of diseases. However, with in-depth research, the therapeutic potential of heparin is being explored beyond anticoagulation. To date, heparin and its derivatives have been tested in the protection against and repair of inflammatory, antitumor, and cardiovascular diseases. It has also been explored as an antiangiogenic, preventive, and antiviral agent for atherosclerosis. This review focused on the new and old applications of heparin and discussed the potential mechanisms explaining the biological diversity of heparin.

A highly active heparinase I from Bacteroides cellulosilyticus: Cloning, high level expression, and molecular characterization

As one of the most extensively studied glycosaminoglycan lyases, heparinase I has been used in producing low or ultra-low molecular weight heparin. Its' important applications are to neutralize the heparin in human blood and analyze heparin structure in the clinic. However, the low productivity and activity of the enzyme have greatly hindered its applications. In this study, a novel Hep-I from Bacteroides cellulosilyticus (BcHep-I) was successfully cloned and heterologously expressed in E. coli BL21 (DE3) as a soluble protein. The molecular mass and isoelectric point (pI) of the enzyme are 44.42 kDa and 9.02, respectively. And the characterization of BcHep-I after purified with Ni-NTA affinity chromatography suggested that it is a mesophilic enzyme. BcHep-I can be activated by 1 mM Ca2+, Mg2+, and Mn2+, while severely inhibited by Zn2+, Co2+, and EDTA. The specific activity of the enzyme was 738.3 U·mg-1 which is the highest activity ever reported. The Km and Vmax were calculated as 0.17 mg·mL-1 and 740.58 U·mg-1, respectively. Besides, the half-life of 300 min at 30°C showed BcHep-I has practical applications. Homology modeling and substrate docking revealed that Gln15, Lys74, Arg76, Lys104, Arg149, Gln208, Tyr336, Tyr342, and Lys338 were mainly involved in the substrate binding of Hep-I, and 11 hydrogen bonds were formed between heparin and the enzyme. These results indicated that BcHep-I with high activity has great potential applications in the industrial production of heparin, especially in the clinic to neutralize heparin.