Last week's announcement that the Palestine Liberation Organization will soon open an office in Nairobi puts the crowning touch on Kenya's move into the Arab sphere of influence.

Recalling that five Palestinians who attempted to shoot down an El Al Jet-liner in Nairobi last year were handed over to the Israelis by Kenyan authorities, a Western diplomat observed, "A lot sure has changed during the past year."

Although regared as one of Israel's chosest friends in black Africa, Kenyas's swing toward the Arabs has been more and more apparent since the March Cairo Afro-Arab summit.

In Cairo, Kenya's vice president, Daniel arap Moi, often mentioned as a leading figure in Kenya's Israel lobby," conferred with the PLO's President Yasser Arafat.

One Keynyan delegate to the Cairo summit said a lot of pressure was exerted on Kenya to unambiguously identify witht the Arab cause.

"It was made quite clear that if we wanted to fully exploit the potential of economic ties with the Arab world, Kenya would have to do much more than we had done so far," he said.

Kenya desperately needs Arab markets to replace the loss of Tanzania, Zambia and Uganda, the three leading African consumers of Kenyan goods.

When Tanzania sealed its border with Kenya earlier this year, it not only cut off Kenyan foodstuffs and manufactured items, but severed land locked Zambia as well. In economic shambles. Idi Amin's Uganda no longer is able to import commidities for ordinary consumers.

kenya also wants Arab investment. Last December, the Saudi Arabian wheeler-dealer. Adnan Khashoggi visited Kenya. He is reportedly interested in investing in tourism, shipping and agribusiness and Kenya's new Arab orientation could speed these and a wide variety of other deals.

Kenya is virtually encircled by hostile states and is growing more politically isolated on a radical-talking continent where its unbirdled capitalism, pro-western sympthies and overties with Israel had made it very much the odd man out. In this context, Kenya is also simply looking for friends.

Arabs could help ease the perpetually strained relations between Kenya and her northern, Soviet-armed neighbor, Somalia. Somalia, which claims a large chunk of Kenyan territory, is a member of the Arab League.

One Arab League state with whom close ties are already well developed is Sudan. A few years ago Sudan, Africa's largest country, was remote from Kenya's consciousness, although the two share a common border.

Now, anti-Communist Sudan is the only neighbor with whom Kenya has any idealogical affinity.

Since attending the Cairo summit, Kenya's foreign minister. Munyua Waiyaki, has been busy cementing ties with other parts of the Arab world. He visited Syria, Iraq and the United Arab Emirates last month and is presently traveling to Egypt and Algeria as well as Sudan. While in Cairo he announced that Kenya would welcome a PLO office in Nairobi.

"This is definitely a success for the Arabs. Kenya is a big prize," and a Western diplomat.

Kenya was one fo the last African states to break relations with Israel after the 1973 war and remains one of three African countries that allow an Israeli interests officer to carry on diplomatic activities. It is the only black African state where Israel's national airline, El Al, still lands.

Since the Cairo summit, the Arabs have opened their first Nairobi bank, the Bank of Credit and Commerce.

Last month, two official Kenyan trade missions traveled to the Middle Easr and increasing numbers of Kenyan businessmen continue to make private visits.

Perhaps the most significant move was the formation last month of the Kenya-Arab Friendship Society. Its chairman is Peter Muigai Kenyatta, the eldest son of President Jomo Kenyatta.

Peter Kenyatta has long been a successful businessman and entered politics several years ago. The move coincided with a expansion of his business interest into the Arab world.

During the past two and a half years, Peter Kenyatta has quietly made six visits to the Middle East concentrating his efforts in Oman, Kuwait and the United Arab Emirates. He is presently airlifting Kenyan meat to these countries and is planning a number of other ventures.

Last November, Peter Kenyatta went public as Kenya's leading advocate of friendship with the Arabs when he hosted a well-publicized dinner for all of the Arab delegates to a U.N. conference here in Nairobi.

Underscoring the importance to Kenya of its growing links with the Arab world, President Kenyatta last month named his son, Peter as assistant foreign minister.

According to an officer of the Kenya-Arab Friendship Society, "There's no doubt that at some point in the future somebody will hint that El Al will have to shut down, "but nobody expects cautions Kenya to move against Israel in the near future.

"The Israealis still have a lot of noted.

Late last week a Foreign Ministry spokesman played down the apparent policy shift, but his minister and assistant minister were unavailable to comment. Peter Kenyatta was conferring with Khermohamed Ali, his partner in the Arab meat business, and Foreign Minister Munyua Waiyaki was in Algers.