Dedicated to our friend and colleague Albrecht Böttcher on the occasion of his 60th birthdayThe paper deals with particular classes of q × q matrix-valued functions which are holomorphic in C \ [α, +∞), where α is an arbitrary real number. These classes are generalizations of classes of holomorphic complex-valued functions studied by Kats and Krein [17] and by Krein and Nudelman [19]. The functions are closely related to truncated matricial Stieltjes problems on the interval [α, +∞). Characterizations of these classes via integral representations are presented. Particular emphasis is placed on the discussion of the Moore-Penrose inverse of these matrix-valued functions.