@article {44421,
	title = {Zinc supplementation decreases galactosylation of recombinant IgG in CHO cells},
	journal = {Applied Microbiology and Biotechnology},
	year = {2018},
	month = {MAY},
	pages = {1-11},
	type = {Journal Article},
	abstract = {<p>Trace element composition of culture medium can be altered to modulate glycoform of recombinant glycoproteins. In this study, we show that Zn2+ supplementation at or above 100 μM decreases galactosylation of recombinant IgG expressed in Chinese Hamster Ovary cells. This decrease in galactosylation is not due to reduced galactosyltransferase expression. This effect persists upon supplementation of galactose and uridine to the culture, indicating that it may not be due to reduced UDP-Gal availability. Measurements of galactosyltransferase activity in the cell lysate show that activity decreases with increasing Zn2+/Mn2+ ratio. This suggests that one possible explanation of the effect of Zn2+ may be reduced intracellular galactosyltransferase activity due to increase in Zn2+/Mn2+ ratio. Consistent with this, the decrease in galactosylation of IgG could be reversed by supplementation of Mn2+ (a cofactor of galactosyltransferase) which increases intracellular Mn2+ content. Measurement of total intracellular Zn2+ content, however, indicates no significant upregulation of total intracellular Zn2+ content and no significant downregulation of intracellular Mn2+ content with Zn2+ supplementation. One possible explanation could be that cellular detoxification response to higher extracellular Zn2+ concentration might lead to changes in intracellular distribution of Mn2+. In this case, Zn2+ supplementation would be expected to interfere with other known effects of Mn2+. Indeed, the previously reported increase in high mannose glycans upon Mn2+ supplementation in the absence of glucose is reversed by Zn2+ supplementation. This study also suggests the use of Mn2+ supplementation as a strategy to overcome the effect of lot-to-lot variability in trace element concentrations on galactosylation.</p>},
	keywords = {CHO cells, glycosylation, manganese, Trace metals, zinc},
	issn = {1757598},
	doi = {10.1007/s00253-018-9064-8},
	author = {Prabhu, Anuja},
	editor = {Gadre, Ramchandra}
}
@article {45593,
	title = {Nickel and cobalt affect galactosylation of recombinant IgG expressed in CHO cells.},
	journal = {BioMetals},
	volume = {32},
	year = {2019},
	month = {OCT},
	pages = {11-19},
	type = {Article},
	abstract = {<p>Glycosylation is an important product quality attribute of antibody biopharmaceuticals. It involves enzymatic addition of oligosaccharides on proteins by sequential action of glycosyltransferases and glycosidases in the endoplasmic reticulum and golgi. Some of these enzymes like galactosyltransferase and N-acetylglucosaminyltransferase-I require trace metal cofactors. Variations in trace metal availability during production can thus affect glycosylation of recombinant glycoproteins such as monoclonal antibodies. Variability in trace metal concentrations can be introduced at multiple stages during production such as due to impurities in raw materials for culture medium and leachables from bioreactors. Knowledge of the effect of various trace metals on glycosylation can help in root-cause analysis of unintended variability in glycosylation. In this study, we investigated the effect of nickel and cobalt on glycosylation of recombinant IgG expressed in Chinese hamster ovary cells. Nickel concentrations below 500 {\textmu}M did not affect glycosylation, but above 500 {\textmu}M it significantly decreases galactosylation of IgG. Cobalt at 50 {\textmu}M concentration causes slight increase in G1F glycans (mono galactosylated) as previously reported. However, higher concentrations result in a small increase in G0F (non galactosylated) glycans. This effect of nickel and cobalt on galactosylation of recombinant IgG can be reversed by supplementation of uridine and galactose which are precursors to UDP-Galactose, a substrate for the enzymatic galactosylation reaction.</p>
},
	keywords = {cobalt, Galactosylation, glycosylation, Nickel, Process variability, Trace metals},
	issn = {0966-0844},
	doi = {10.1007/s10534-018-0152-0},
	author = {Prabhu, A. and Gadgil, M.}
}
@article {47584,
	title = {Trace metals in cellular metabolism and their impact on recombinant protein production},
	journal = {Process Biochemistry},
	volume = {110},
	year = {2021},
	month = {NOV},
	pages = {251-262},
	type = {Review},
	abstract = {Replacement of serum and increasing use of chemically defined media demands optimisation of trace metal components for biomanufacturing applications. Trace metal availability can impact culture performance, productivity and product quality. Several trace metals are cofactors of metabolic and other enzymes, and thus their availability regulates cellular metabolism. Additionally, they can also affect the availability of other trace metals and stability of some medium components. Such factors also need to be considered while formulating trace metal concentrations in the culture medium. Due to their very low concentrations, these components are susceptible to substantial variability arising from contaminants from other raw material and leaching from process equipment and can contribute to process variability. Understanding the role and impact of trace metals will help develop strategies to achieve targeted process parameters and increase process robustness vis-{\textquoteleft}a-vis any lot-to-lot variability in trace metal concentration in culture medium. This review describes the role of trace metals, particularly manganese, copper and zinc, in central carbon metabolism to aid in understanding the basis of metal-mediated effects on culture performance and provides a comprehensive review of the reported impact of trace metals on CHO cell culture performance and recombinant protein quality.},
	keywords = {Chinese hamster ovary cells, glycosylation, Medium formulation, Process variability, Product quality, Recombinant proteins, Trace metals},
	issn = {1359-5113},
	doi = {10.1016/j.procbio.2021.08.006},
	author = {Prabhu, Anuja and Gadgil, Mugdha}
}
