Biological Oxidation Characteristics Of The Silkworm,Bombyx Mori During Diapause Initiation

At 25℃,the oxygen consumption of diapause eggs of silkworm,Bombyx mori increased significantly before diapause initiation,whereas it decreased rapidly after diapause initiation.The initiation of diapause can be prevented by instant hydrochloric acid soaking(HCl)but its molecular mechanism is still unclear.The main indicators of aerobic oxidation metabolism during the diapause initiation stage of diapasue eggs of silkworms,Bombyx mori were examined systematically in the present study to explore the biological oxidation characteristics of diapause eggs during the diapause initiation stage.The main results are reported as follow:I.PK,PDH,SDH,SCR,AS,AS,CS and NADH regulated aerobic oxidation coordinately in diapause eggs of silkworm,Bombyx mori during 0 to 72 h after oviposition.The levels of Pyruvate kinase(PK),pyruvate dehydrogenase(PDH),succinate dehydrogenase(SDH),Complex II(SCR),ATP synthase(AS),acetyl-Co A(AC),citrate synthase(CS)and reduced nicotinamide adenine dinucleotide(NADH)in diapause eggs gradually increased during 0 to 72 h after oviposition,and gradually decreased after diapause initiation.The initiation of diapause was prevented by instant hydrochloric acid soaking,in company with the changes of the trend about above indicators,which was in accordance with the changes in respiratory oxygen consumption.It showed that the above indicators affect respiratory oxygen consumption by regulating aerobic oxidation.II.Nicotinamide adenine dinucleotide(NAD)was the leading indicator of the change of oxygen oxidation in the diapause eggs of the silkworm,Bombyx mori during 18 to 30 h after oviposition.During 18 to 30 h after oviposition,glucose(GLC),α-pyruvate dehydrogenase(α-KGDH)and NAD were the leading indicators of glycolysis(EMP),tricarboxylic acid cycle(TCA)and Oxidative Phosphorylation,respectively,which were significantly changed at 20 h,23 h,and 19 h after oviposition,respectively.It demostrated that NAD content was the leading indicator of aerobic oxidation in diapause eggs during the diapause initiation.III.Rate-limiting enzymes,substrates or products of aerobic oxidation of diapause eggs of the silkworm,Bombyx mori during the initiation of diapause3-phosphoglycerate kinase(PGK)and pyruvate(PA)were the rate-limiting enzyme and product of the EMP pathway,respectively.Isocitrate dehydrogenase(ICDHm)and NADH were the rate-limiting enzyme and product of the TCA pathway,respectively.The ATP synthase(AS)and adenosine triphosphate(ATP)were the rate-limiting enzyme and product of the Oxidative Phosphorylation,respectively.Among them,1/26 AS had the lowest activity,and 1/30 ATP had the lowest content.It demostrated that AS was the key rate-limiting enzyme that regulated aerobic oxidation.The actual rate in three stages of aerobic oxidation had a character of decreasing progressively.