Error in Update and Set statement

Dear Folks,

How to handle the below error, please suggest. I have migrated my database
from oracle to postgres through Ora2PG then I am getting this error for
function.

If I am writing the code for every column which are within set (column
name1, column name2, etc) then it's running successfully but if there are
so many columns with set then how can I handle this because in below code
there are 7 column with set statement and we have to write very big code
for this. Please suggest how to handle this situation.

ERROR: syntax error at or near "SELECT"
LINE 2: ...LEAD_TIME,ITEM_NUMBER,ORDER_UOM_CODE,ORDER_QTY) =(SELECT LIN...
^
********** Error **********

ERROR: syntax error at or near "SELECT"
SQL state: 42601
Character: 123

Code as below:

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update ppo_master_detail set (LINE_STATUS,LINE_TYPE,PROMISE_DATE,
LEAD_TIME,ITEM_NUMBER,ORDER_UOM_CODE,ORDER_QTY) =(SELECT LINE_STATUS,
LINE_TYPE,PROMISE_DATE,LEAD_TIME,ITEM_NUMBER,ORDER_UOM_CODE,ORDER_QTY
from ppo_master_detail where subscriber_id = 65 and
row_number=supplierdetail.row_number
and po_number=supplierdetail.po_number and
company_id=supplierdetail.company_id )
where po_number =PONum.po_number and company_id=PONum.company_id and
subscriber_id = 65 and row_number=supplierdetail.row_number;
--iRowCounter:=iRowCounter+1;

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