Dr. Oksoo Han                                                                                          TOP A. Molecular Mechanistic Studies on the Biosynthesis of Jasmonic Acid.
   Jasmonic acid has been proposed to play a role in the response to pathogens and wounding by inducing expression of several genes including proteinase inhibitors, vegetative storage proteins, and lipoxygenase enzymes. Our primary interests are molecular mechanistic studies and engineering of lipoxygenase and allene oxide synthase in the jasmonic acid biosynthetic pathway. We have characterized stress responsive biphasic expression pattern of lipoxygenase and currently working on development of stress-resistant transgenic plant.
B. Mechanistic Studies and Engineering of Protoporphyrinogen Oxidase
   Protoporphyrinogen Oxidase, the last common enzyme in the biosynthesis of heme and chlorophyll, catalyzes the conversion of protoporphyrinogen IX into protoporphyrin IX by six-electron oxidation. It is generally accepted that protoporphyrinogen oxidase is the primary target of diphenyl ether herbicides such as oxyfluorfen and acifluorfen. Among protoporphyrinogen oxidase known from animals, plants and bacteria, the one from B. subtilis is resistance to diphenyl ether herbisides. Therefore, protoporphyrinogen oxidase from B. subtilis is an ideal choice to be introduced into plants for producing herbicide-resistant transgenic plants. We have produced diphenyl ether-resistant transgenic rice and are currently working on the engineering of protoporphyrinogen oxidase.
C. Genetic Engineering of Erythromycin Biosynthetic Enzymes
   Erythromycin A, a clinically valuable anti-infective drug, is produced by Saccharopolyspora erythrea. Structurally, it consists of a 14-membered macrolactone ring and two deoxysugars, L-cladinose and D-desosamine. Because of medical and commercial importance, its biosynthetic genes are extensively studied, including polyketide synthase genes and 6-deoxyerythronolide B hydroxylase gene. We are interested in engineering of 6-deoxyerythronolide B hydroxylase (Cytochrome P450eryF) and TDP-6-Deoxy-L-threo-D-glycero-4-hexulose epimerase.

Dr. Ro-Dong Park                                                                                    TOP
A. Mechanistic Studies of Rice B-N-Acetylhexosaminidase
B-N-Acetylhexosaminidase catalyzes the hydrolysis of terminal nonreducing N-acetyl-D-hexosamine residues in N-acetyl-B-D-hexosaminides occurred in microbial cell wall. It has been described as an emerging target for the design of low-molecular weight antifungals since the last decade. We have purified and characterized the B-N-acetylhexosaminidase from rice to screen and develop the reaction-based B-N-acetylhexosaminidase inhibitors, and are currently working on the engineering of the protein for the enzyme structure-based rational approaches.
B. Characteristics, Mode of Action, and Classification of Microbial Chitosanases
Our primary interests are molecular mechanistic studies and engineering of a chitosanase purified from Bacillus sp. P16, which was isolated from environmental samples as a source of potent chitosanase. We have characterized the physicochemical properties, and the optimum and stability conditions for enzyme activity. We also interested in the classification of the enzyme based on the amino acid sequence, substrate specificity, and splitting patterns. We are currently working on the engineering of the protein.
C. Chitooligosaccharides and Their Derivatives as New Biofunctional Materials
Chitooligosaccharides, the hydrolytic products from chitin and chitosan, have become biofunctional and valuable produces. The known functions include anti-bacterial, anti-tumoric, immunomodulating and wound healing. We interested in modification of the chitooligosaccharides using enzymes to produce more bio-potent derivatives for application, especially in agricultural field.
Selected Publications
H.J. Kim, H.C. Lee, J.S. Oh, B.A. Shin, C.S. Oh, R.D. Park, K.S. Yang, and C.S. Cho. Polyelectrolytic
   complex composed of chitosan and sodium alginate for wound dressing application. J. Biometerial
   Science Polymer E. 10: 543-556, 1999
R.D. Park, K.C. Cho, Y.Y. Jo, K.W. Jang, K.Y. Kim, J.H. Shim, Y.W. Kim, Y.T. Suh. Changes in the
   distribution and activity of N-acetyl-B-D-hexosaminidase and chitinase during cultivation of soybean
   sprouts. J. Chitin Chitosan 5:9-14, 2000
R.D. Park, K.Y. Kim, J.H. Shim, K.J. Jo, and Y.Y. Jo. Purification and reaction mechanism of
   chitosanase from Bacillus sp. P16. in Proceedings of 8th ICCC and 4th APCCS (Japan), 208, 2000
R.D. Park and Ju-Lan Jin. Characterization, mode of action, classification of microbial chitosanase. J.
   Chitin Chitosan 5: 207-216, 2000