1. Effect of norleucine on mycelial fragmentation in Cephalosporium acremonium
S W Drew, D J Winstanley, A L Demain Appl Environ Microbiol. 1976 Jan;31(1):143-5. doi: 10.1128/aem.31.1.143-145.1976.
DL-Norleucine, which is known to replace methionine for stimulation of cephalosporin C formation, also mimics methionine's effect on arthrospore formation. Thus, hyphal fragmentation, like antibiotic biosynthesis, is divorced from a sulfur donation role.
2. Effect of inhibitors of cell envelope synthesis on beta-sitosterol side chain degradation by Mycobacterium sp. NRRL MB 3683
L Sedlaczek, B M Górmiński, K Lisowska J Basic Microbiol. 1994;34(6):387-99. doi: 10.1002/jobm.3620340605.
The role of the lipid bilayer and the peptidoglycan of the mycobacterial cell wall in the permeation of beta-sitosterol into the cell and its transformation to androst-1-ene-3,17-dione (AD) and androsta-1,4-diene-3,17-dione (ADD) was studied. Specific inhibitors were used at concentrations affecting the biosynthesis of the assumed target structures, but causing only partial cell growth inhibition or exerting no effect on growth. m-Fluorophenylalanine and DL-norleucine which are known to disorganize the biosynthesis of amphipatic components of the outer layer of the lipid bilayer, used at concentrations 250 micrograms/ml and 400 micrograms/ml, respectively, increased the formation rate of AD+ADD from 0.3 (control) to 0.7 and 0.8 mg products/g dry weight/h. The disorganization of the underlying mycolyl-arabinogalactan structure by the action of the ethambutol at the concentration 40 micrograms/ml, at which the cell growth was apparently not affected, caused the decrease of the product formation from 135 mg/l to 70 mg/l. In the presence of isoniazid (350 micrograms/ml) only trace amounts of AD accumulated during 48 hours of transformation indicating much lower activity than that of the intact cells. The most effective among the tested inhibitors of peptidoglycan synthesis were glycine (15 mg/ml) and vancomycin (150 micrograms/ml) which enhanced the transformation activity of the treated cells nearly three times. Increased transformation rate was also obtained by the action of colistin at concentrations ranging from 10 micrograms/ml to 15 micrograms/ml.
3. Sulfur metabolism of a mutant of Cephalosporium acremonium with enhanced potential to utilize sulfate for cephalosporin C production
K I Komatsu, R Kodaira J Antibiot (Tokyo). 1977 Mar;30(3):226-33. doi: 10.7164/antibiotics.30.226.
Characteristics of a mutant of Cephalosporium acremonium with enhanced potential to utilize sulfate for cephalosporin C production were investigated with sulfur-starved cells. DL-Norleucine showed an inhibitory effect on cephalosporin C and penicillin N production by the mutant in the presence of a sulfur source such as sulfate, sulfite, thiosulfate, and L-cystine, but it exhibited no effect when it was added after a certain period of incubation. On the contrary, antibiotic production by the parent was stimulated by norleucine regardless of the addition time. An increase in the intracellular cysteine pool was found when the cells were incubated with L-methionine or norleucine and sulfate. Enzymatic studies revealed that methionine and norleucine stimulated the cysteine desulfhydrase formation, and this effect was significant in the mutant. Finally the mutant was found to have an enhanced L-serine sulfhydrylase activity. The increase in this enzyme activity in the mutant seems responsible for the increase in the sulfate-utilizing ability and the methionine sensitivity by maintaining a high level of the cysteine pool. Accordingly, the effect of methionine and norleucine is assumed to be exerted through cysteine.
