N-Glycosylation and enzymatic activity of the rHuPH20 expressed in Chinese hamster ovary cells

Structural identification and quantification of unreported sialylated N-glycans in bovine testicular hyaluronidase by LC-ESI-HCD-MS/MS

Bovine testicular hyaluronidase (BTH), which accelerates the absorption and dispersion of drugs by decomposing hyaluronan in subcutaneous tissues, has been used in medical applications, including local anesthesia, ophthalmology, and dermatosurgery. The requirement of N-glycans for the activity of human hyaluronidase has been reported, and BTH has greater activity than human hyaluronidase. However, the N-glycan characteristics of BTH are unclear. From a commercial BTH source containing additional proteins, purified BTH (pBTH) was obtained using size exclusion chromatography, and the structures and quantities of its N-glycans were analyzed using liquid chromatography (LC)-electrospray ionization-higher energy collisional dissociation (HCD)-tandem mass spectrometry (MS/MS). In pBTH, 32 N-glycans were identified, with 12 sialylations (39.0% of total N-glycan content), nine core-fucosylations (31.5%), six terminal galactosylations (14.6%), five high-mannosylations (13.7%), and four bisecting N-acetylglucosamine structures (7.8%). The presence of sialylated glycopeptides in pBTH was confirmed by nano-LC-HCD-MS/MS analysis. The absolute quantity of all N-glycans was calculated as 1.4 pmol (0.6 pmol for sialylation) in pBTH (1.0 pmol). The sialylation level (related to half-life, thermal stability, resistance to proteolysis, and solubility) was 24.4 times higher than that of human hyaluronidase. The hyaluronan degradation activity of de-sialylated pBTH decreased to 41.2 ± 4.2%, showing that sialylated N-glycans were required for pBTH activity as well. This is the first study to identify and quantify 32 N-glycans of pBTH and investigate their structural roles in its activity. The presence of larger amounts of sialylated N-glycans in pBTH than in human hyaluronidase suggests a greater utilization of pBTH.

Identification, quantification, and structural role of N-glycans in two highly purified isoforms of sheep testicular hyaluronidase

Animal-derived hyaluronidase, which hydrolyzes the polysaccharide hyaluronic acid, has been used in medical applications despite its limited purity. Additionally, the N-glycan characterization of sheep testicular hyaluronidase (STH) and its structural role remain poorly understood. In this study, STH was purified from the commercially available STH preparation (containing at least 14 impurity proteins) using heparin-affinity chromatography followed by size exclusion chromatography. The structure and quantity of N-glycans of STH were investigated using liquid chromatography-electrospray ionization-high energy collision dissociation-tandem mass spectrometry. Two isoforms, H3S1 and H3S2, of STH were obtained (purity >98 %) with a yield of 3.4 % and 5.1 %, respectively. Fourteen N-glycans, including nine core-fucosylated N-glycans (important for the stability and function of glycoproteins), were identified in both H3S1 and H3S2, with similar quantities of each N-glycan. The amino acid sequences of the proteolytic peptides of H3S1 and H3S2 were compared with those reported in STH. The hyaluronic acid-degrading activity of deglycosylated H3S1 and H3S2 was reduced to 70.8 % and 71.1 % compared to that (100 %) of H3S1 and H3S2, respectively. This is the first report of N-glycan characterization of two highly purified isoforms of STH. These H3S1 and H3S2 will be useful for medical use without unwanted effects of partially purified STH.

Strategies for Glycoengineering Therapeutic Proteins

Almost all therapeutic proteins are glycosylated, with the carbohydrate component playing a long-established, substantial role in the safety and pharmacokinetic properties of this dominant category of drugs. In the past few years and moving forward, glycosylation is increasingly being implicated in the pharmacodynamics and therapeutic efficacy of therapeutic proteins. This article provides illustrative examples of drugs that have already been improved through glycoengineering including cytokines exemplified by erythropoietin (EPO), enzymes (ectonucleotide pyrophosphatase 1, ENPP1), and IgG antibodies (e.g., afucosylated Gazyva®, Poteligeo®, Fasenra™, and Uplizna®). In the future, the deliberate modification of therapeutic protein glycosylation will become more prevalent as glycoengineering strategies, including sophisticated computer-aided tools for "building in" glycans sites, acceptance of a broad range of production systems with various glycosylation capabilities, and supplementation methods for introducing non-natural metabolites into glycosylation pathways further develop and become more accessible.