الفهرس 
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Abstract
Actinobacteria are considered one of the most important bioactive metabolite producers especially genus Streptomyces. The present work involves a comparative study on S. avermitilis the producer of AVM and its derivatives. Avermectins (AVMs) and their naturally ocurring analogues, milbemycins (MILs), ivermectin (IVE) and abamectin (ABA) represent one of the most developed antiparasitic agents. The main goal of the study was the identification and optimization of fermentation conditions responsible for improvement the production of AVM from Egyptian isolate of S. avermitilis. The qualitative and quantitative analysis of AVM was carried out by Thin-layer chromatography (TLC) and 6538 QTOF with Agilent 1290 UHPLC. Results showed that optimization conditions were carried out by using production medium containing 30 g/L corn starch, and 0.725 g/L CaCO3, pH 7, 8% inoculum size and incubated at 32.5°C. LC–MS-based approach was applied to study the metabolite and proteome profiles of local strain MN368133 and ATCC 31267 S. avermitilis at different fermentation time points. The aim is to reveal a difference in production of AVM and its derivatives depending on starch as carbon source and find out which gene products and metabolic pathways are responsible for production in both isolates. Eleven genes were detected in proteomic analysis AveD, AveF, AveC, AveBIII, AveBII, AveBI, AveA1, AveA2, AveA3, AveA4, AveE extracted at SDS-PAGE patterns for two isolates. The preferable carbon was corn and soluble starch for both isolates. The ATCC 31267 showed the highest similarity matching with gene products from S. avermtilis (GenBank NCBI taxonomic identifier 33903) which shows 99% and 80% of sequence identity for all genes. The prediction model for C5 methyltransferse predicted ligands with two S-adenosyl-l-homocysteine (SAH); attached sites were detected using pymol software at 25 residues at 4A, The SAH as a ligand, binding two different pockets on the surface of this protein. The active site showing 13 molecules forming glycine almost are parallel beta sheets and 12 molecules representing two alpha sheets. The Probity Score, 2.11 showing the clash score with 8.34 as high contacts between atoms A236 HIS-A238 ASN), (A38 TYR-A58 LEU).The total length of the residues is 260 with 11 secondary structures helices labeled with H1, H2, and strands by their sheets A, B. There are four hydrogen interactions between the atom number 1418, 1428, 1431, 1442 within the chain A interacting with 3266, 3255, 3252, 3242 within chain B and showing distance 2.85, 2.89, 2.95 and 2.84. There are two ligands attached to C5- ketoreductase; NADP nicotinamide-adenine-dinucleotide phosphate and rabelomycin. There are 6 hydrophobic reactions in the chain A between 159A, 162A, 202A with distance ranges from 3.27 to 3.90. The hydrogen bonds were among the residues 158A, 159A, 170A and 200A with distance 2.62 to 3.28. As hydrophobic interactions result from entropic changes rather than attractive forces between atoms, there are no clear geometries of hydrophobic association. A large family of membrane-bound microsomal enzymes, which catalyze the transfer of glucuronic acid to a wide variety of exogenous and endogenous lipophilic substrates. The length of the chromosome 9,025,608 bp with coding genes 7,583 and 88 noncoding genes.The metabolic processes involved in primary metabolism such as carbon and amino metabolism were the dominant category. Most TCA cycle enzymes were expressed, but several glycolytic enzymes were repressed. This was deduced to be correlated with the composition of the culture medium, and higher glucose concentration during AVM production will decrease the production. The high expression of leuC, which was involved in leucine biosynthesis, further confirmed the leucine as possible precursor of AVM. High expression of many genes such as Sun, which is DNA activator binding protein that had hardly been in the cells with high glucose concentration. The process includes many enzymatic reactions with different enzymes such as acyltransferase (AT), ketosynthase (KS) and ketoreductase (ER).The interaction between the target proteins, which includes 11 nodes, which represent the target protein and each edge, represents protein- protein interaction; the average node degree is 3.89. The AveA1 is the query proteins and first shell of interactions is centrally located in the PPI, P-value is 0.0036 and the average local clustering coefficient is 0.874 so the network has significantly more interaction than expected. The peaks of AVM with RT 6.2 were detected in the ATCC 31267 isolate metabolic filtrate with all types of carbon sources at the 10th day of incubation time. However, the peaks were detected in the Egyptian isolate especially the samples with corn and wheat as carbon source at the 8th and 10th day of incubation time. The ATCC 31267 and Egyptian isolate showing the up and down regulated metabolomic features.