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Kim, Hoyeun,Na, Sang ,Hyeon,Lee, So-Young,Jeong, Young-Min,Hwang, Hyun-Ju,Hur, Jae ,Young,Park, Sang-Hyun,Woo, Je-Chang,Kim, Sang-Gu Portland Press Ltd. 2012 The Biochemical journal Vol.443 No.1
<P>TDP1 (tyrosyl-DNA phosphodiesterase 1), a member of the PLD (phospholipase D) superfamily, catalyses the hydrolysis of a phosphodiester bond between a tyrosine residue and the 3′-phosphate of DNA. We have previously identified and characterized the <I>AtTDP</I> gene in <I>Arabidopsis thaliana</I>, an orthologue of yeast and human <I>TDP1</I> genes. Sequence alignment of TDP1 orthologues revealed that AtTDP has both a conserved C-terminal TDP domain and, uniquely, an N-terminal SMAD/FHA (forkhead-associated) domain. To help understand the function of this novel enzyme, we analysed the substrate saturation kinetics of full-length AtTDP compared with a truncated AtTDP mutant lacking the N-terminal FHA domain. The recombinant AtTDP protein hydrolysed a single-stranded DNA substrate with <I>K</I><SUB>m</SUB> and <I>k</I><SUB>cat</SUB>/<I>K</I><SUB>m</SUB> values of 703±137 nM and (1.5±0.04)×10<SUP>9</SUP>M<SUP>−1</SUP>·min<SUP>−1</SUP> respectively. The AtTDP-(Δ1–122) protein (TDP domain) showed kinetic parameters that were equivalent to those of the full-length AtTDP protein. A basic amino acid sequence (RKKVKP) within the AtTDP-(Δ123–605) protein (FHA domain) was necessary for nuclear localization of AtTDP. Analysis of active-site mutations showed that a histidine and a lysine residue in each of the HKD motifs were critical for enzyme activity. Vanadates, inhibitors of phosphoryl transfer reactions, inhibited AtTDP enzymatic activity and retarded the growth of an <I>Arabidopsis tdp</I> mutant. Finally, we showed that expression of the <I>AtTDP</I> gene could complement a yeast <I>tdp1</I>Δ<I>rad1</I>Δ mutant, rescuing the growth inhibitory effects of vanadate analogues and CPT (camptothecin). Taken together, the results of the present study demonstrate the structure-based function of AtTDP through which AtTDP can repair DNA strand breaks in plants.</P>
Hypoglycemic Effects of Germinated Rough Rice Extract in Streptozotocin-induced Diabetic Rats
Youn Ri Lee,In Guk Hwang,Koan Sik Woo,Hyun Young Kim,Dong Sik Park,Jae Hyun Kim ,Yun Bae Kim,Junsoo Lee,Heon Sang Jeong 한국식품영양과학회 2011 Preventive Nutrition and Food Science Vol.16 No.3
The hypoglycemic effects of germinated rough rice extract in streptozotocin (STZ)-induced diabetic rats were investigated. Weight gain was significantly lower in the diabetic groups than in the normal control (NC); however, they were higher in the 1% and 3% diabetic groups given germinated Goami2 rough rice extract (DM-3%GGRRE) than in the diabetic control (DC). While food intake in all diabetic groups was significantly higher than that of the NC, there was no significant difference among all diabetic groups. The weight percentages of liver and kidney in all diabetic groups were significantly higher than that of the NC. In terms of blood glucose, the diabetic group showed about a three times larger value than the normal group. Moreover, in the 3% germinated rough rice extract group, the blood glucose level became lowered. The levels of alanine transaminase, aspartate transaminase, blood urea nitrogen, creatinine phosphokinsae, and creatinine increased in general with the induction of diabetes using STZ; however, the 3% GGRRE-treated group displayed a significant decrease in these levels compared to the diabetic group. The results show that the 3% GGRRE, rather than the 1% GGRRE, was considerably more effective at reducing blood glucose and improving impaired glucose tolerance, suggesting the germinated rice extracts may play a role in preventing liver and kidney damage.