Nov 1 (Reuters) - Australia's ReadyTech Holdings said on Tuesday it had received a buyout offer worth A$481.4 million ($308.3 million) from Pacific Equity Partners (PEP), one of the country's biggest private-equity firms, sending its shares to a three-month high.

But the offer has already received pushback from ReadyTech's second-largest investor, Microequities Asset Management, which has flagged it would not support the takeover.

The A$4.50-per-share proposal, an almost 39% premium to the stock's last close, marks the third play for an Australian technology company in the past week, highlighting increasing interest in the sector amid cheap valuations.

Shares of ReadyTech advanced as much as 26.5% to A$4.10 on Tuesday.

ReadyTech said Pemba Capital Partners, its largest investor with 32.01% of its shares, and PEP would seek to obtain the Australian corporate regulator's go-ahead for the companies to work together on the proposal.

Microequities Chief Executive Officer Carlos Gil, whose firm owns 13.2% of ReadyTech, said the PEP offer was not enough to win his support.

"It was a very quick decision in our investment committee to say no," Sydney-based Gil told Reuters by telephone.

"It is such an unattractive price that it was a unanimous agreement that we could not support this ... We think it's an unfair price and nowhere near what we think the company is worth."

ReadyTech did not immediately respond to a Reuters request for comment, while PEP declined to comment.

PEP was granted due diligence access and discussions were ongoing, New South Wales-based ReadyTech said, but no arrangement has been reached about the value, structure or terms of any potential deal.

The takeover bid is the third for an Australian technology company in the past week with Nitro Software receiving an almost $A500 million offer from KKR's Alludo on Monday.

Last week, ELMO Software agreed a A$500 million bid from Los Angeles-based K1 Investment Management.

($1 = 1.5615 Australian dollars) (Reporting by Scott Murdoch in Sydney and Upasana Singh in Bengaluru; Editing by Devika Syamnath and Sherry Jacob-Phillips)