The Commodity Futures Trading Commission authorized the New York Stock Exchange yesterday to get into the commodity business and open its own New York Futures Exchange.

The federal commodity agency approved trading regulations for the new exchange and authorized NYFE to begin buying and selling contracts for future delivery of five foreign currencies.

The New York Futures exchange -- already nick-named "knife" by the industry -- probably will go into operation next month. The New York Stock Exchange's directors are expected to choose the opening day of the subsidiary at their board meeting next week.

NYFE will enter the futures market with 1,500 members -- more than any commodity market except the big Chicago grain centers -- but with only five commodities to trade.

The exchange has applications pending at the CFTC to trade futures on U.S. Treasury bills and notes in addition to its contracts for pounds, Swiss francs, marks, Canadian dollars and yen.

Also pending is a plan for NYFE to merge with the American Commodity Exchange, known as ACE. A subsidiary of the American Stock Exchange, ACE has failed to attract enough business to be profitable and several months ago began looking for a merger partner.

An agreement to merge ACE and NYFE was announced several weeks ago. Since then, ACE has received new offers from the New York Commodity Exchange. Since its silver-market collapsed two months ago, volume on Comex has dwindled, raising questions about whether it can survive as an independent market.

Financial futures allow investors to speculate on, or protect themselves against, changes in interest rates or currency values, just as grain futures reflect future prices for grain.