Pakistan Research Repository


Aziz, Farhat (2004) LIPASES MULTIFUNCTIONAL ENZYMES. PhD thesis, University of Karachi, Karachi.



With the aim of searching some) unique triacylglycerol ester hydrolases "LlPASES" from our ecosystem we have started our project with screening of lipase producing bacteria. Out of 124 Gm +ve different isolates including Bacilli and Staph, 30 strong lipase producers were screened out & subjected to comparative study. These 30 isolates were catagorized into 7 different groups based on nutritional requirements by the help of dendogram derived from hierarchical agglomerative clustering. Initially different edible oils were used as substrates during plate assay, TLC & GC/MS analysis of lipase activity. On the basis of the results of TLC, 18 isolates (from 7 nutritional groups) were further classified into four subgroups depending upon the biochemical potentials including enzyme activity & substrate specificity. Variety of catalytic activities i.e ydrolysis, esterification, substrate specificity (including fatty add, glyceride & specially Sn specificity) and bio-transforming abilities of lipase were examined successfully by using standard substrates. As different products of lipase activity have been found very important in different industries especially pharmaceuticals, agrochemicals, oleochemical etc. So by keeping in mind their medicinal & commercial value we have ransacked successfully highly versatile lipases from spore forming Bacilli (5Va) "the most diversified", Clinical isolates (C1.6 & C1.16) and environmental isolates (RC.9) of Staph. The lipase of 5Va (heat & alkaline pH resistant) presumably produces isozymes. Its ability to transform different substrates into different products like alcohols (e.g cyclohexanol) & dicarboxylic acid (e.g adipic acid) make this enzyme significant for food industry as well as for human physiology. Cyclization & lactonization were also found to be the characteristic features for the organic synthesis. Apart from these, its ability to hydrolyze phospholipids & synthesis of cyclopropane ring containing compound & oxirans may reflect its few damaging aspects related to pathogenesis. It can also be used as biodehydrogenating agent in oleochemical industry. In addition, this study gave us some important lipases of Staph isolates which might play a key role in pharmaceutical because of their following capabilities. 1. Synthesis of arachidic acid & cyclopentyl ring containing compounds, the possible precursors of arachidonic acid e.g CI.6 and RC.9. 2. Hydrolysis of broad substrate range of lipcc of CI.16 play important role in hydrolysis of serum TG & dietary fats. Its presize activity on 18 carbon F.A. in case of lipcc & lipcr seems to be important feature in oleo chemical industries. 3. Highly resistant isolates to high temperature (41°C) & alkaline pH 9.2 might play some role in different industries like in laundry detergents. Active binding site of these enzymes seem to be amphipathic in nature. They can interact with variety of substrates. Different catalytic activities of these lipase seem to be dependent on inducing condition, environmental condition & substrates. Their enhanced activity on higher carbon fatty acids shows its easy penetration into more thick lipid layers which might play some role to reduce the environmental pollution. For hydrolysis, specificity was observed for Sn1 & Sn3 positions and for recemization specificity was observed for Sn-2 position.. The shifting of acyle groups presumably occurred from Sn-2 to Sn-1 position. For 5Va (Bacillus) recemization seems to be conditional. Behavior of these lipases (except RC.9) as "true lipase" seem to be iducer dependent. Finally we can say that as a result of this research we have got some interesting inducible lipases, may benefit human being in many aspects. Physiological aspects: I.Products of lipolytic activity may serve as transcriptional factors, activators of cellular fur cellular" messenger for signal transduction. II. Synthesis of arachidic acid & cyclopenty ring containing compounds (possible precusor of arachidonic acid) may effect the hormonal balance & can up regulate oncogenes. III. They may replace the mammalian lipases to hydrolyze serum VLDL &TG moiety & could be use in digestive drugs. Aspects related to pathogenesis: I.Hydrolysis of phospholipids have shown that lipases may serve as invasive factor. II.Synthesis of oxirans may result hyper immune reactions. Commercial Aspects: I.Hydrolysis of long chain saturated F.As (solid lipids), presize hydrolysis of 18:1 may use in splitting & restructuring of natural TG., easy penetration into lipid layer (due to independence to surface tension & viscosity), dehydrogenation & dehydrogenation by Bacillary lipase may contribute great role in oleo chemical industry. II.The synthesis of sibling compounds having benzene ring in structure presumably benefit the petroleum industry to prepare petroleum products easily on large scale by using bacterial source. III. Synthesis of menthol (cyclohexanol) by 5Va lipase will help to replace the use of eukaryotic lipase. IV. The synthesis of other unique cyclic compounds not reported before may contribute in pharma industry provided their effect on human physiology will prove significant & presumably play remarkable role in drug designing.

Item Type:Thesis (PhD)
Uncontrolled Keywords:lipases, enzymes, staph isolates, lipolytic activity, bacillus, staphylococci
Subjects:Biological & Medical Sciences (c) > Biological Sciences(c1) > Microbiology(c1.8)
ID Code:1245
Deposited By:Mr. Muhammad Asif
Deposited On:18 Jan 2007
Last Modified:04 Oct 2007 21:05

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