INCORPORATION OF TYROSINE CARBOXYL GROUPS AND UTILIZATION OF D-TYROSINE IN MELANOGENESIS

The tyrosine carboxyl incorporation and d-tyrosine utilization in vertebrate melanogenesis were determined experimentally and calculated mathematically. A given skin enzyme preparation was incubated simultaneously with differently labeled tyrosines as substrates. The indirect determination of tyrosine carboxyl incorporation was best demonstrated and calculated with the use of l-tyrosine-1-14C and uniformly labeled l-tyrosine-14C without the complication of d-tyrosine utilization. Similar results were obtained by utilizing dl-tyrosine-2-14C and l-tyrosine-1-14C if d-tyrosine utilization was not involved. The d-tyrosine utilization was indirectly estimated by utilizing l-tyrosine-1-14C, uniformly labeled l-tyrosine-14C, and dl-tyrosine-2-14C. © 1969.