Why were the ottomans able to control trade on Silk Road

Throughout the Middle Ages, Constantinople, capital of the Eastern Roman Empire (known as the Byzantine Empire), was the trade hub between the goods transported along the Silk Road all the way from China, and the Venetian and Genoese merchants. When Constantinople was conquered by the Ottomans by the force of arms, in 1453 A. D. they took over the control of all the trade coming through the Silk Road. However, they denied European merchantes access to Constantinople and the goods traded in that city which prompted the Portuguese to seek maritime routes to India and China sailing around the Western African coastline.