Metabolic Analysis of the Asparagine and Glutamine Dynamics in an
Industrial CHO Fed-Batch Process
Abstract
Chinese Hamster Ovary (CHO) cell lines are grown in cultures with
varying asparagine and glutamine concentrations, but further study is
needed to characterize the interplay between these amino acids. By
following 13C-glucose, 13C-glutamine, and 13C-asparagine tracers using
metabolic flux analysis (MFA), CHO cell metabolism was characterized in
an industrially relevant fed-batch process under glutamine supplemented
and low glutamine conditions during early and late exponential growth.
For both conditions MFA revealed glucose as the primary carbon source to
the tricarboxylic acid (TCA) cycle followed by glutamine and asparagine
as secondary sources. Early exponential phase CHO cells prefer glutamine
over asparagine to support the TCA cycle under the glutamine
supplemented condition, while asparagine was critical for TCA activity
for the low glutamine condition. Overall TCA fluxes were similar for
both conditions due to the trade-offs associated with reliance on
glutamine and/or asparagine. However, glutamine supplementation
increased fluxes to alanine, lactate and enrichment of glutathione,
N-Acetyl-Glucosamine (NAG) and pyrimidine-containing-molecules. The late
exponential phase exhibited reduced central carbon metabolism dominated
by glucose, while lactate reincorporation and aspartate uptake were
preferred over glutamine and asparagine. These 13C studies demonstrate
that metabolic flux is process time dependent and can be modulated by
varying feed composition.