@article { ISI:000245519000057,
	title = {Tryptophan residue is identified in the substrate binding of penicillin G acylase from Kluyvera citrophila},
	journal = {Enzyme and Microbial Technology},
	volume = {40},
	number = {5},
	year = {2007},
	month = {APR},
	pages = {1389-1397},
	publisher = {ELSEVIER SCIENCE INC},
	type = {Article},
	address = {360 PARK AVE SOUTH, NEW YORK, NY 10010-1710 USA},
	abstract = {<p>Penicillin acylases are important enzymes in pharmaceutical industry for the production of semi-synthetic beta-lactam antibiotics via the key intermediate 6-aminopenicillanic acid. The penicillin G acylase purified from Kluyvera citrophila (KcPGA) on modification with tryptophan-specific reagents such as N-bromo succinamide (NBS) and 2-hydroxy 5-nitrobenzylbromide (HNBB) showed partial loss of activity and substrate protection. Various solute quenchers and substrate were used to probe the microenvironment of the putative reactive tryptophan through fluorescence quenching. Homology modeling of KcPGA structure has been carried out. Docking substrate on this modeled KcPGA structure identifies the tryptophan residue that is directly influenced by substrate binding. To confirm the biological significance of this particular tryptophan, we did a sequence comparison of PGAs from various organisms. The sequence alignment clustered the matches into two sets, those closer to (\&gt; 40\% identical) KcPGA and had the tryptophan of interest present in them formed the first set, while those less identical (\&lt; 30\%) to KcPGA and the particular tryptophan absent in them formed the second set. It is clear from the reported kinetic parameters of representative members of these two sets that the affinity for penicillin G (penG) of the former class is several times better. Thus, based on our studies we suggest that the tryptophan residue in the identified position is important for binding substrate penG by the acylases. (c) 2006 Elsevier Inc. All rights reserved.</p>},
	keywords = {fluorescence measurement, K. citrophila, Penicillin G acylase, sequence alignment, substrate-docking, tryptophan modification},
	issn = {0141-0229},
	doi = {10.1016/j.enzmictec.2006.10.022},
	author = {Kumar, R. Suresh and Prabhune, Asmita and Pundle, A. V. and Karthikeyan, Muthukumarasamy and Suresh, C. G.}
}
@article { ISI:000261133600023,
	title = {Structural features of Penicillin acylase adsorption on APTES functionalized SBA-15},
	journal = {Microporous and Mesoporous Materials},
	volume = {116},
	number = {1-3},
	year = {2008},
	month = {DEC},
	pages = {157-165},
	publisher = {ELSEVIER SCIENCE BV},
	address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS},
	abstract = {<p>The immobilization of Penicillin acylase (PGA) enzyme (which belongs to the Ntn hydrolase super family) into the amino-functionalized SBA-15 mesoporous molecular sieve is carried out to see the effect of silica as a host matrix on the enzyme kinetics. Physicochemical characterization by nitrogen adsorption, powder XRD and TEM methods indicate that the characteristic hexagonal features and the original pore structure of the parent SBA-15 is retained even after the incorporation of PGA. The adsorption of PGA on SBA15 shows a dependence on the pore volume and the composition of the adsorbent. The maximum loading of the enzyme was observed at pH 7.8, slightly below the isoelectric point of the enzyme. The loading capacity of immobilized PGA is 34 mg protein per 0.5 g of SBA-15. The trapped enzyme is more stable than the soluble form to temperature and pH environments and retained 73\% of its activity after immobilization. This enhanced stability is attributed to the protective nature of the cage itself and to the rigidity of the SiO(2) matrix, which reduces the freedom of peptide-chain refolding of molecular motions that occur in denaturation processes. The strength of binding is very strong; however, the activity of the immobilized enzyme is then simply restored with very little leakage of enzyme from the support. An important feature of the immobilized PGA enzyme is the excellent reusability without significant loss in activity, which indicates potentially exciting industrial/biomedical application of this support. (C) 2008 Elsevier Inc. All rights reserved.</p>},
	keywords = {Penicillin G acylase, PGA immobilized SBA-15, pH and temperatures stability, SBA-15},
	issn = {1387-1811},
	doi = {10.1016/j.micromeso.2008.03.030},
	author = {Shah, Pallavi and Sridevi, N. and Prabhune, Asmita and Ramaswamy, Veda}
}
