Regulation and routes of biosynthesis of serine and arginine in Methylophilus methylotrophus AS1

Whole cell extracts and partially purified enzyme preparations of the obligate methylotroph Methylophilus methylotrophus AS1 have been studied for the presence of key enzymes of serine and arginine synthesis. Arginine biosynthesis proceeds via the N‐acetylornithine glutamate transacetylase pathway, as found in the fluorescent pseudomonads. Serine synthesis proceeds by the phosphorylated pathway, as in Escherichia coli. There is no evidence for the repression of enzyme synthesis in either of these pathways, however, strict feedback inhibition occurs for the first step in each pathway.