Penalbumin (PEN), a newly discovered sulfhydryl-containing glycopmtein from egg whites
of penguins (Sphenisciformes), is a major constituent of all penguin egg whites studied, but
it is low or very low in most other egg whites studied. Adelie penguin (Pygoscelis adeliae)
egg white contains -30% ovaIbumin (POVAL) and 25% PEN, while chicken egg white
contains ~55% ovalbumin (COVAL) and <0.01% PEN. PEN has a molecular weight
of 61,000 and contains 15% carbohydrate and two sulfhydryl groups, but no phosphates.
POVAL has a molecular weight of 48,000 and eontains 7% carbohydrate, three sulfhydryl
gmups, and one phosphate. Penguin serum albumin (PSA) has properties which are very
similar to bovine serum albumin (BSA), and the composition and properties of PEN were
suggestive of an ancestral relationship to POVAL and COVAL. PEN reacts slowly with
5,5'-dithiobis(2-nitrobenzoic acid) (DTNB), while PO VAL reacts rapidly. On simultaneous
addition of DTNB and eystamine (B,~'-diaminodiethyl disulfide) the rate oj e reaction with
PEN was increased, but not with POVAL
