Sotheby’s, the auction house under pressure from activist investors to boost profit, doubled the amount it can borrow to make art loans in a bid to win clients and top consignments.

Sotheby’s secured a credit line of more than $1 billion to make such loans from a consortium including General Electric Capital Corp., according to a filing last week. The New York-based auction house previously could borrow as much as $550 million under that line.