China's central bank on Tuesday said it will allow banks to cut the minimum required mortgage down payment to 20 per cent from 25 per cent for first-home purchases as it steps up support for the property market. Reviving investment in real estate is crucial for the government, which cut interest rates six times since late 2014. Shanghai government-backed Greenland Holdings Corp Ltd is one of two Chinese issuers that Moody's has rated at the lowest investment-grade with a negative outlook. The other firm is state-owned China National Gold Group Corp. Moody's currently rates 20 Chinese companies one level above junk. Among them, 20 per cent had negative outlook or were on review for downgrades compared with 5 per cent at the end of 2014. "Fallen angels are a major risk for investors this year," said Owen Gallimore, a credit analyst at Australia & New Zealand Banking Group Ltd.