A securities firm must explain a Boesky payment.

The Securities and Exchange Commission has issued subpoenas to the privately held New York securities firm, Jamie Securities, and to the firm’s chief stock trader, John A. Mulheren, to determine whether there was anything improper about $500,000 paid by the firm to stock speculator Ivan F. Boesky. The SEC’s review of Jamie’s payments and its probe of Jamie’s overall relationship to Boesky are part of a broad look at the ties that Boesky had to various Wall Street firms. Jamie, which is backed by well-known investors, including Canada’s Belzberg family, is believed to have executed some of its trades through a firm controlled by Boesky.