JAPAN LONG-TERM PRIME SEEN CUT TO RECORD LOW SOON Japan's long-term banks will soon cut their prime rate, now at a record low 5.5 pct, by 0.2 or 0.3 percentage point in response to falling secondary market yields on their five-year debentures, long-term bankers said. The long-term prime rate is customarily set 0.9 percentage point above the coupon on five-year bank debentures issued by the long-term banks every month. The latest bank debentures, at 4.6 pct, have met strong end-investor demand on the prospect of further declines in yen interest rates, dealers said. The current 5.5 pct prime rate has been in effect since February 28.