select based on multi-column primary keys

I have set up a table with a multi-column primary key constraint:

CREATE TABLE iopoints
(
enclosureid numeric(3) NOT NULL,
pointid char(4) NOT NULL,
equipmentgroup varchar(64) NOT NULL,
deviceid varchar(8),
devicetype varchar(24),
operationdesc varchar(64) NOT NULL,
entrytime timestamp NOT NULL DEFAULT ('now'::text)::timestamp(6) with
time zone,
systemid numeric(3) NOT NULL,
CONSTRAINT "ID" PRIMARY KEY (systemid, enclosureid, pointid)
)
WITHOUT OIDS;

If I had a row in the table where systemid=123, enclosureid=ab,
pointid=56, I would have a Primary Key ("ID") of 123ab56 for that row.

I now want to run a select based on the Primary Key, something like:

SELECT * FROM iopoints WHERE ID = 123ab56

Is something like this even possible? Or am I forced to do:

SELECT * FROM iopoints WHERE systemid=123 AND enclosureid=ab AND pointid=56

I have searched high and low but can not find a syntax example of how to
select based on a multi-column primary key, any tips?

Thanks,

mawrya