Bioprocess Engineering 2nd Edition by Fikret Kargi,Michael Shuler

Exercise 4

Consider the pathway in Fig. 4A.1 for production of lysine, methionine, isoleucine, and
theronine. You need to produce lysine. Describe a strategy for making large amounts of ly-
sine. Your strategy can consist of adding various amino acids to the medium and choosing the
mutant cells altered in regulation. Say you can identify up to two points of mutation (e.g., re-
moval of feedback inhibition). Figure 4A.1 A simplified diagram of the aspartate pathway in E. coli. Each solid arrow
designates a reaction catalyzed by one enzyme. The biosynthetic products of the pathway
(in boldface) are all allosteric inhibitors of one or more reactions. Careful study of this diagram reveals that with a single exception (the inhibition exerted by valine) the inhibition
imposed by one amino acid does not cause starvation for a different amino acid. Part (a)shows the regulatory interrelationships of the L-lysine, L-methionine, and L-isoleucine
branches of the pathway. Part (b) shows the regulatory interrelationships of the
L-isoleucine, L-valine, and L-leucine branches