Two threonine dehydratases, I and II, were found to occur in Euglena gracilis and each enzyme was purified partially. Like the biosynthetic threonine dehydratases of other organisms, dehydratase I was feedback-inhibited by isoleucine and not affected by adenylates. Dehydratase II was not influenced by branched-chain amino acids and adenylates. Occurrence of dehydratase II, with a much higher activity than dehydratase I, suggests that dehydration of threonine is not the key point in the regulation of isoleucine biosynthesis in E. gracilis.
BradfordM. M.1976; A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein-dye binding. Analytical Biochemistry 72:248–254
BryanJ. K.1980; Synthesis of the aspartate family and branched-chain amino acids. In The Biochemistry of Plants, A Comprehensive Treatise, Amino Acids and Derivatives5 pp. 403–452MiflinB. J.
Edited by New York: Academic Press;
KovalevaS. V.,
DorozhkoA. I.,
BelyaevaN. F.,
KaganZ. S.1981; Certain properties of biosynthetic l-threonine dehydratase from subcellular structures of the brewers’ yeast Saccharomyces carlsbergensis. Ukrainskiǐ biokhimicheskiǐ zhurnal 53:31–37
MiyajimaR.,
ShiioI.1972; Regulation of aspartate family amino acid biosynthesis in Brevi-bacterium flavum. VI. Effects of isoleucine and valine on threonine dehydratase activity and its formation. Journal of Biochemistry 71:951–960
OdaY.,
NakanoY.,
KitaokaS.1982b; The mechanism of growth inhibition by threonine in Euglena gracilis: regulation of isoleucine-valine biosynthesis by 2-oxobutyrate. Archives of Microbiology 132:22–25
OdaY.,
NakanoY.,
KitaokaS.1982c; Properties and regulation of valine-sensitive acetolactate synthase from mitochondria of Euglena gracilis. Journal of General Microbiology 128:1211–1216
ShiioI.,
OzakiH.1981; Feedback inhibition by methionine and S-adenosylmethionine, and desensitization of homoserine O-acetyltransferase in Brevibacterium flavum. Journal of Biochemistry 89:1493–1500
SquiresC. H.,
LevinthalM.,
De FeliceM.1981; A role for threonine deaminase in the regulation of α-acetolactate biosynthesis in Escherichia coli K12. Journal of General Microbiology 127:19–25