Massachusetts Mutual Life Insurance Company has completed a previously announced purchase of First Mercantile Trust Company from SunTrust Banks Inc.

First Mercantile, Memphis, sells record-keeping and investment-management services to 3,100 retirement plans with a total of about 140,000 participants and $5 billion in assets under management, according to SunTrust, Atlanta.

MassMutual has a $40 billion retirement plan business.