Mustafa Koç, the boss of the largest industrial conglomerate in Turkey, Koç Holding, died Thursday in an Istanbul hospital following a heart attack at age 55, announced his doctors.

“We lost Mustafa Koç following a heart attack which he suffered at his home, despite all the efforts of the doctors,” he told reporters a doctor of the American Hospital of the Nisantasi area. CEO fainted during a workout. He had suffered last year a gastric surgery and lost about 40 kg, the Turkish media reported.

Mustafa Koç led since 2003 one of the strongest and most respected companies of Turkey, founded in 1920 by his grandfather Vehbi Koç.

Vehbi Koç was born July 20, 1901 in Ankara in a family of the working class. Like the Sabanci family, he turned the Armenian private property in 1942 including that of Margarios Ohanyan.

By itself, the family group and Koç hundred companies provide 9% of Turkish exports and 8% of gross domestic product (GDP).

Koç Holding has the particular Tüpras oil company, which owns one of the largest refineries in Europe and a major automotive cluster in Turkey that produces models of Fiat and Ford brands. He is also active in the banking sector.

The boss of Koç Holding had suffered the wrath of the government of the current Islamic-conservative President Recep Tayyip Erdogan, especially after he criticized the repression of political slingshot June 2013. His group had particularly suffered significant tax adjustments.