Lipases are ubiquitous enzymes which catalyze the hydrolysis of fats into fatty acids and glycerol at the waterlipid interface and reversing the reaction in non-aqueous media. Lipases occupy a place of prominence among biocatalysts owing to their novel and multifold applications in oleochemistry, organic synthesis, detergent formulation and nutrition. Lipase was extracted and isolated from the alimentary canal and digestive gut of Catla catla (catla). The tissue was homogenized in a ratio of 1:3 with starting buffer (0.01 M TrisHCl, pH 7.2). The crude extract thus obtained was precipitated using ammonium sulphate (20-80%). Excess salt was removed by Dialysis and the resultant dialysate (Desalted Enzyme) was subjected to DEAE-Cellulose column for Ion Exchange Chromatography at a flow rate of 0.5 ml/min. Elution was carried out by a step gradient of NaCl (100-800 mM) in the starting buffer. Active fractions were pooled as Purified Fraction (PF) and were used for physical characterization of pH, temperature and effect of calcium on the enzyme activity, structural characterization, molecular characterization and for kinetic studies. The Purified Fraction (PF) showed final specific activity of 1438.72 U/mg. The optimum pH was 7.8 and the optimum temperature was found to be 20˚C. Melting Temperature (T m) value was 42˚C and the activation energy of purified lipase was 34.82 KJ/mol/K. Thermal stability of lipase was found to be at 20˚C. Lipase activity retained up to 3 h of incubation with 10 mM and 20 mM of CaCl 2 in starting buffer. This shows that Calcium has enhancing property from the denaturation of enzyme. Michaelis-Menten constant (K m) of lipase from Indian major carp, catla for the hydrolysis of pNPP was 6.695 mM. Turnover number (k cat) of lipase (catla) was 0.0022 s-1. Catalytic efficiency (k cat /K m) of lipase was 0.0003412 s-1 mM-1. SDS-PAGE of purified lipase (PF) revealed a homogenous single band with molecular mass of 70 kDa. Secondary structural arrangement of α helices and β strands of purified lipase results 48.51% and 9.74%, respectively using Circular Dichroism.
Transcription elongation is one of the key steps at which RNA polymerase II‐directed expression of protein‐coding genes is regulated in eukaryotic cells. Different proteins have been shown to control this process, including the ELL/EAF family. ELL Associated Factors (EAFs) were first discovered in a yeast two‐hybrid screen as interaction partners of the human ELL (Eleven nineteen Lysine‐rich Leukemia) transcription elongation factor. Subsequently, they have been identified in different organisms, including Schizosaccharomyces pombe. However, no homolog(s) of EAF has as yet been characterized from plants. In the present work, we identified EAF orthologous sequences in different plants and have characterized two novel Arabidopsis thaliana EAF homologs, AtEAF‐1 (At1g71080) and AtEAF‐2 (At5g38050). Sequence analysis showed that both AtEAF‐1 and AtEAF‐2 exhibit similarity with its S. pombe EAF counterpart. Moreover, both Arabidopsis thaliana and S. pombe EAF orthologs share conserved sequence characteristic features. Computational tools also predicted a high degree of disorder in regions towards the carboxyl terminus of these EAF proteins. We demonstrate that AtEAF‐2, but not AtEAF‐1 functionally complements growth deficiencies of Schizosaccharomyces pombe eaf mutant. We also show that only AtEAF‐1 displays transactivation potential resembling the S. pombe EAF ortholog. Subsequent expression analysis in A. thaliana showed that both homologs were expressed at varying levels during different developmental stages and in different tissues tested in the study. Individual null‐mutants of either AtEAF‐1 or AtEAF‐2 are developmentally normal implying their functional redundancy. Taken together, our results provide first evidence that A. thaliana also possesses functional EAF proteins, suggesting an evolutionary conservation of these proteins across organisms.
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