Structure elucidation methionine

The structural elucidation of factor F 430 (134) is based to a large extent on biosynthetic investigations with 5-aminolevulinic acid (18) and methionine (142) 83a,b). The peripheral methyl groups in positions 2 and 7 stem from C-methionine (142). 5-Aminolevulinic acid (18)... 

Next to trypsin chymotrypsin is the most preferred proteolytic enzyme in sequencing. Its specificity is less absolute than that of trypsin. Primarily the bonds that follow phenylalanine, tyrosine and tryptophan are cleaved, but measurable hydrolysis takes place next to leucine and methionine residues as well. It is advisable, therefore, to determine in preliminary experiments the conditions (enzyme-substrate ratio, time, temperature) best suited for the formation of a few and well separable fragments. Occasionally also less specific enzymes, such as pepsin, papain or thermolysin find application in structure elucidation. For the hydrolysis of specific bonds new microbial proteases can be isolated. There are known prolidases and also enzymes which hydrolyze solely the bond which follows a pyroglutamyl residue and so on. 

The diketopiperazine cycZo-(L-proline-L-thioproline) (498) was isolated from Tedania ignis but a bacterial origin for the metabolite was suggested [423]. Cyc/o-(L-proline-L-methionine) (499) was isolated from Pseudomonas aeruginosa associated with the Antarctic sponge, Isodictya setifera. The structure was elucidated by spectroscopic methods and confirmed through synthesis [424],... 

Biosynthetic studies have indicated a mixed polyketide-terpenoid origin for the unusual fungal metabolite andobenin (51) (Scheme 8). The two extra methyl groups ( ) are derived from methionine. Andobenin co-occurs with andilesin (52) whose structure has been recently elucidated by X-ray and c.d. analysis. ... 

The elucidation of the structure of vitamin Bj2 was a tour de force of the early days of X-ray diffraction and was recognized in 1964 by the award of the Nobel Prize to Dorothy Hodgkin. The coenzyme Bj2 acts in concert with a variety of enzymes that catalyze reactions of three main groups. In the first, two substituents on adjacent carbon atoms, -X and -H, are permuted, this is called the isomerase reaction. In the second type, methylcobalamin methylates a substrate, as in the conversion of homocysteine to methionine, for example. Finally, B j2 is also involved... 

Methylthioadenosine (MTA) represents one of the main products of S-adenosylmethionine (Ado-Met) metabolism and is distributed ubiquitously in micromolar amounts in several prokaryotes and eukaryotes . Although the chemical structure of this thioether was elucidated in 1924, its biological role as product of methionine metabolism was demonstrated by Schlenk in 1952, even before the discovery of its precursor Ado-Met. ... 

After the structure was elucidated, considerable attention was centered on the biosynthesis of this antibiotic. According to the original proposal (Birch et al., 1958), the methynolide was thought to be derived from acetate, and then the methyl groups were introduced from methionine or similar donor. The trans-... 

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