S. Pluschkell et al., KINETICS OF GLUCOSE-OXIDASE EXCRETION BY RECOMBINANT ASPERGILLUS-NIGER, Biotechnology and bioengineering, 51(2), 1996, pp. 215-220
The kinetics of glucose oxidase (GOD) excretion by recombinant Aspergi
llus niger NRRL-3 (GOD3-18) were investigated using enzymatic activity
measurements as well as gel electrophoresis techniques. The majority
of GOD was produced during rapid growth in the first phase of the cult
ivation. The high excretion rate during this phase did not prevent the
endocellular accumulation of GOD up to 40% of the total soluble cell
protein demonstrating that the production rate exceeded the excretion
rate of the enzyme into the culture medium. During the second phase of
the cultivation, excretion of GOD occurred at a slower rate, although
the majority of GOD produced during the first phase was excreted duri
ng the second phase of the cultivation. At the end, about 90% of the t
otal GOD produced was recovered from the culture medium. Two-dimension
al gel electrophoresis provided evidence that endo- and exocellular GO
D were indistinguishable, revealing identical posttranslational modifi
cations (e.g., signal sequence cleavage, glycosylation pattern). The r
esults demonstrate that the initial steps of the secretory pathway are
fast and that the excretion of the enzyme into the culture fluid was
most likely delayed due to retention by the cell wail. (C) 1996 John W
iley & Sons, Inc.