Folate-dependent enzymes. V. Role of tryptophan in dihydrofolate reductase

Fluorine-19 nuclear magnetic resonance studies of ligand binding to 3-fluorotyrosine- and 6-fluorotryptophan-containing dihydrofolate reductase from Lactobacillus casei

“…The effects of methotrexate and NADPH on this resonance are somewhat less than additive, and the experiments with the "fragments" show that its shift is influenced by both the 2,4-diaminopyrimidine and the paminobenzoyl-L-glutamate moieties. A single tryptophan residue has been implicated in the activity of dihydrofolate reductase by chemical modification studies of the enzyme from E. coli (Williams, 1975), S.faecium (Warwick et al, 1972), and from two strains of L. casei (Liu and Dunlap, 1974; dramatic (greater than 1000-fold) reduction in the affinity of the enzyme for NADPH (K. Hood and G. C. K. Roberts, unpublished work). It is tempting to suggest that this tryptophan residue corresponds to the fluorotryptophan Wmf, but definitive conclusions must await NMR studies of the chemically modified enzyme.…”

Properties of the purified extracellular cholesterol oxidase from Rhodococcus equi No. 23

“…These findings suggest that SH groups may be involved in the catalytic activity of the enzyme, as shown in the enzyme from B. sterolicum (Uwajima et al, 1974). The high sensitivity of the purified enzyme to TV-bromosuccinimide might depend on the oxidation of cysteine residue, although there are some possibilities that the loss of enzyme activity resulted from oxidation of tryptophan residue (Warwick et al, 1972).…”

Reaction of dihydrofolate reductase with dansyl chloride. Chemical modification of a sensitive lysine residue and fluorometric studies of the dansylated enzyme

“…Tryptophan residues have been implicated in the active centers of dihydrofolate reductases from L. casei (Liu and Dunlap, 1974), as well as from chicken liver (Freisheim and Huennekens, 1969) and amethopterin-resistant strains of S'. faecium (Warwick et al, 1972) and E. coli (Greenfield, 1974).…”