I can mainly think of car companies but I am sure there are more. Anyway BMW, Mercedes, VW (and its subsidaries), Porsche and a lot more all excited as German was split. Knowing that the east was struggling financially, what did these companies do during the cold war. Were they all part of the west which allowed them to progress into the giants they are today? Were there similar competitors in the east that failed? Did the western companies merge with the eastern? Did the companies split with Germany and then merged in the 90s?
BMW: Munich
VW: Wolfsburg
Mercedes: Stuttgart
All of them were West German companies.
To the roots of your question: There were big East German companies, but all of them were so called "VEB"s, "Volkseigene Betriebe" (companies owned by the people). So they were state owned and when the GDR "collapsed" (reunification with West Germany), the VEBs were privatized by law.