GT Global's head of emerging-market debt portfolios Michael Mabbutt is quitting to set up his own business.
GT's emerging-market debt funds will be managed from New York by Craig Munro, from the end of this month.
Mabbutt manages about $560m spread through the Dublin-based GT emerging markets bond fund, Austrian-based GT emerging markets bond fund II and US-based GT global high-income fund.
He is also responsible for $440m of emerging-market debt in other GT Global funds.
Two emerging-market debt analysts based in London will continue their present roles but report to Munro in New York.
Communications manager Alex Campbell says more than 65 per cent of the group's emerging-market debt money is sourced from the US.