* Q2 profit up 40.5 pct
* Investment banking up 42.2 pct on higher M&A
* Shares up marginally premarket (Adds second-quarter details, background, share move)
June 19 (Reuters) - Jefferies Group LLC on Tuesday reported a 40.5 percent jump in quarterly profit as strength in its investment banking business, which advises on deals and listings, helped offset weakness in its trading unit.
The company's investment banking revenue rose 42.2 percent to $500.3 million in the second quarter, helped by an increase in equity and debt underwriting, as well as mergers and acquisition advisory.
New York-based Jefferies, which usually kicks off the earnings season for U.S. investment banks, is widely seen as an indicator of the performance of big Wall Street banks.
Big U.S. banks have already warned that second-quarter market activity has decreased from the first quarter, but are upbeat on investment banking.
Goldman Sachs last month said it expects robust activity across investment banking. It also said IPO activity, particularly in the United States and China's tech sector, was picking up.
Total sales and trading revenue of Jefferies slipped 10.7 percent to $295.1 million in the second quarter, echoing JPMorgan's warning that trading revenue would fall versus a year ago.
Net income attributable to Jefferies rose 40.5 percent to $98 million in the quarter ended May 31.
Shares of Jefferies were marginally higher at $22.80 in premarket trading.
Jefferies' net revenue rose to $822.6 million from $779.3 million.
Total non-interest expenses rose 5.7 percent to $700.7 million.
This is Jefferies' first quarterly results after Leucadia, its former parent, shed most of its non-financial assets to become a pure-play investment banking and advisory business. (Reporting by Aparajita Saxena and Diptendu Lahiri in Bengaluru; Editing by Maju Samuel)