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Research was conducted to determine the action of fosfomycin on MurA enzyme and the effect of amino acid substitution on its activity. Results show that fosfomycin inhibits the enzyme and the inhibitory effect is altered when cysteine residue is replaced with aspartate-117.

Guanosine pentaphosphate synthetase I (GPSI) from Streptomyces antibioticus is an enzyme with properties similar to a polynucleotide phosphorylase (PNPase) from Escherichia coli. The enzyme is capable of synthesizing guanosine tetraphosphate. It catalyzes the polymerization of ADP, the phosphorolysis of poly(A) and the synthesis of guanosine pentaphosphate. dCDP stimulates the GPS activity of GPSI while the PNPase activity is inhibited. A study clones and sequences the gene responsible for the GPSI synthesis.

The horseradish peroxidase-based enzyme-linked immunosorbent assay based on chemiluminescence analysis with an Amerlite analyzer effectively detects the production of extracellular peroxidase in actinomycetes. An analysis of 39 strains by this method identified five strains producing a large amount of peroxidase. Spectrophotometric assay of Streptomyces strain EC 22 and S. thermoviolaceus shows that detection of 2,4-dichlorophenol oxidation is the most sensitive and reproducible method for determining peroxidase activity.

Genetic and sequence analysis indicates that the His212, His268, and Asp214 endogenous ligands form the ferrous active site of isopenicillin N synthase (IPNS) from Streptomyces jumonjinensis. Mutations in these residues remove enzymatic activity. The fourth ligand is a glutamine residue that is probably replaced when the substrate binds to the enzyme. Enzymatic activity is unaffected by site directed mutagenesis of the other histidine residues and aspartic acid residues which are conserved in bacterial and fungal IPNS. These substitutions produce no observable conformational changes.

The changes in the signal peptide, xylanase A, affects the level of its production in Streptomyces lividans. The removal of the signal peptide or a change in its cleavage site stops secretion of the enzyme. Substitution of the signal peptide with those of xylanase B, cellulase A, mannanase or acetylxylan esterase has no effect on enzyme production. Substitution with the signal peptides of cellulase B, xylanase C, and LamB decreases enzyme formation. The difference in production is due to the nature of the signal sequences as all the clones have the same transcription levels.