Developmental program of PGK-1 and PGK-2 isozymes in spermatogenic cells of the mouse: Specific activities and rates of synthesis☆

[摘要] Thespecificactivitiesandsynthesisoftheubiquitousisozyme,PGK-1,andthetestis-specificisozyme,PGK-2,havebeenquantitatedandlocalizedinspermatogeniccellsofthemouse.ThereisafivefoldincreaseintotalPGKspecificactivitybetweenimmatureandadulttesteswhichbeginsatapproximately30daysofage,coincidentwiththeappearanceoflate-middlestagespermatids.TheincreaseintotalPGKisentirelyduetotheappearanceandincreaseofthePGK-2isozyme.RatesofPGKsynthesisweremeasuredbylabelingtesticularcellsinvitrowith[3H]leucineandpurifyingthePGKisozymes.Whentotaltesticularcellswereexamined,PGK-2synthesiswasdetectableafter22daysofageatverylowlevelsandincreasedinoldertestestoalevelof0.5%oftotalproteinsynthesis.PGK-1synthesisremainedrelativelyconstantatallagesatalevel100-foldlower(0.005%).Testicularcellswereseparatedintohighlyenrichedfractionsofparticularspermatogenicstagesbycentrifugalelutriation.ThePGK-1synthesisrateswere,again,verylowandnotsignificantlydifferentbetweenthevariousspermatogenicstages.PGK-2synthesiswaslowtonondetectableinpachytenespermatocytes,increasedto0.07%inearlyspermatidsandrepresented0.7%oftotalproteinsynthesisinlatespermatids.ThisincreasedrateofPGK-2synthesisappearstorequireanincreaseintheamountofPGK-2mRNAinlatespermatids,cellsinwhichnoactiveRNAsynthesisisdetectable.

[学科分类] 生物科学（综合）