Gene Coding for Enzymes

Many enzymes are involved in the synthesis of secondary metabolites. The modular biosynthetic enzymes polyketide synthase (PKS) and nonribosomal peptide synthetase (NRPS) are responsible for the generation of a multitude of structurally diverse and biologically important small-molecule natural products. A complex carbon structure is assembled sequentially from simple carbon building blocks (acyl-CoA and amino acids). The elongation of each carbon unit is catalyzed by 

---

Moreover, as expected disruption of genes coding for enzymes critical to the function of osteoclast such as tartrate-resistant acid phosphatase (Hayman et al., 1996) and cathepsin K (Gowen et al., 1999) also produced osteopetrosis. This complements earlier discussed spontaneous osteopetrotic phenotypes produced by interception of pathways generating either protons or chloride necessary for mineral dissolution. 

The bacterial reverse mutation test (Ames Test) investigates the ability of chemicals and drags to induce reverse (back) mutations in bacteria, which involves base pair substitutions additions and/or deletions (frameshift mutations) of one or a few DNA base pairs. The bacterial strains used in the test system have mutations in genes coding for enzymes required for the biosynthesis of the amino acids histidine (Salmonella typhimurium) and tryptophan (Escherichia coli). If... 

In potato and cassava, there is no clear evidence yet for the existence of more than one isoform. Antisense experiments in potato tuber did not eliminate BE activity completely. If there were two genes coding for enzymes, antisense neutralization if one of them would not affect the expression of the other. However, this result is inconclusive because antisense experiments usually decrease the amounts of the protein encoded but do not reduce it to zero. Purification and characterization of the remaining activity in antisense experiments could resolve the matter, but was not done in this particular case. 

The use of co-trimoxazole in HIV-positive patients has been associated with a high rate of hypersensitivity reactions (40-80%), attributed to the bioactivation of the sulfonamide component, sulfamethoxazole, to its toxic hydroxylamine and nitroso metabolites. In a study of HIV-positive patients with (n = 56) and without n — 89) hypersensitivity to co-trimoxazole, functionally significant polymorphisms in the genes coding for enzymes involved in co-trimoxazole metabolism were unlikely to have been major predisposing factors in determining individual susceptibility to co-trimoxazole hypersensitivity (179). 

Genes coding for enzymes involved in post-translational modification of autoantigens... 

Furthermore, it may be likely that highly resistant strains with chromosomal mutations may also have genes coding for enzymes that modify streptomydn. 

Enzyme induction A mechanism whereby the genes coding for enzymes needed to metabolize a particular nutrient are activated by the presence of that nutrient. 

Enzyme repression Mechanism by which the presence of a particular metabolite represses the genes coding for enzymes used in its synthesis. 

Mori K, Blackshear PE, Lobenhofer EK, Parker JS, Orzech DP, Roycroft JH, Walker KL, Johnson KA, Marsh TA, Irwin RD, Boorman GA (2007) Hepatic transcript levels for gene coding for enzymes associated with xenobiotic metabolism are altered with age. Toxicol Pathol 35 242-251... 

Resistance to thiopeptide antibiotics can be generated by a variety of mechanisms. In the producing streptomycetes, there are genes coding for enzymes that methylate the 2 -OH of adenosine 1067 in the 23S rRMA (38,39). This methylation confers resistance to... 

---