β-hydroxy Pyruvic acid is a metabolite in the process of photorespiration in plants.[1] In peroxisomes, hydroxypyruvate is reduced to glycerate by NADH.[2] [3]

Reference:
[1]. Stafford, H.A., Magaldi, A., and Vennesland, B. The enzymatic reduction of hydroxypyruvic acid to D-glyceric acid in higher plants. J. Biol. Chem. 207(2), 621-629 (1954).
[2]. Douce, R., and Heldt, H.-W. Photorespiration. Photosynthesis: Physiology and Metabolism 9, 115-136 (2000).
[3]. Givan, C.V., and Kleczkowski, L.A. The enzymic reduction of glyoxylate and hydroxypyruvate in leaves of higher plants. Plant Physiol. 100(2), 552-556 (1992).