Source annotation pipeline provenance for Ldhb annotations including catalytic activity; oxidoreductase activity; oxidoreductase activity, acting on the CH-OH group of donors, NAD or NADP as acceptor.

Source annotation pipeline provenance for Ldhb annotations including L-lactate dehydrogenase (NAD+) activity; mitochondrial inner membrane.

Source annotation pipeline provenance for Ldhb annotations including L-lactate dehydrogenase (NAD+) activity; lactate metabolic process; mitochondrion; pyruvate catabolic process.

Source annotation pipeline provenance for Ldhb annotations including identical protein binding; membrane raft; oxidoreductase complex.

Source annotation pipeline provenance for Ldhb annotations including NAD binding; NAD+ metabolic process.

Source annotation pipeline provenance for Ldhb annotations including L-lactate dehydrogenase (NAD+) activity; cytoplasm; cytosol; lactate metabolic process; mitochondrial inner membrane.

Source annotation pipeline provenance for Ldhb annotations including L-lactate dehydrogenase (NAD+) activity; cytosol; identical protein binding; lactate metabolic process; membrane raft; and 1 other terms.

This publication is the original_reference for four GOA IDA annotations to Ldhb (L-lactate dehydrogenase (NAD+) activity, lactate metabolic process, NAD+ metabolic process, NAD binding), but its cached abstract concerns nandrolone decanoate effects on pentose-phosphate-pathway and malate-aspartate-shuttle enzymes (G6PD, 6-phosphogluconate dehydrogenase, malic enzyme, NADP-linked isocitrate dehydrogenase, transketolase, NAD-linked malate dehydrogenase) and does not mention lactate dehydrogenase. Full text is unavailable; these four annotations are marked UNDECIDED until the full text can be checked.

For Ldhb, this publication was reviewed as context for kinase binding.

A low-abundance LDHB isoform (LDHBx) is produced by translational readthrough that appends a conserved hidden PTS1 peroxisome-targeting signal, directing at least ~1.6% of total cellular LDHB to peroxisomes; LDHBx can also co-import LDHA, supporting peroxisomal redox-equivalent regeneration. The mechanism is conserved across mammals (Rats is a MeSH term). This minor peroxisomal pool is documented here and retained as a suggested question; it is not asserted as a GO:0005777 (peroxisome) annotation for rat Ldhb, because the comparator check finds no peroxisome annotation in GOA for human LDHB, mouse Ldhb or human MDH1 (the other readthrough-peroxisome case) and a rat ISS would have no annotated source.

For Ldhb, this publication provides evidence/provenance for direct annotations to lactate dehydrogenase activity and contextual annotations to identical protein binding; protein binding.

Rat LDHB is the heart-type (LDH-H) subunit of lactate dehydrogenase (EC 1.1.1.27), an NAD(H)-dependent oxidoreductase catalyzing the reversible interconversion of pyruvate and L-lactate coupled to NADH/NAD+, with LDHB favoring the lactate-to-pyruvate direction.

LDHB-associated direction is lactate to pyruvate with NAD+ reduced to NADH, while LDHA is commonly discussed as catalyzing the reverse direction.

Mammalian LDH is a tetramer assembled from the two principal subunits LDHA (muscle-type, M) and LDHB (heart-type, H), forming homotetramers and heterotetramers that tune glycolysis and redox balance.

LDHB-rich (LDH-1, heart-type) isoenzymes have lower KM values for pyruvate (~0.1 mM) and NADH (~0.04 mM) than LDHA-rich (LDH-5) isoenzymes, consistent with specialization for lactate handling in oxidative tissues such as heart.

LDHB is predominantly cytosolic, positioned at the end of glycolysis to regenerate NAD+ and interconvert lactate/pyruvate, shaping cytosolic redox balance.

A minor peroxisomal LDHB pool (LDHBx) is generated by translational readthrough that adds a hidden PTS1 signal; at least ~1.6% of cellular LDHB is targeted to peroxisomes and LDHBx can co-import LDHA, supporting peroxisomal redox-equivalent regeneration. This mechanism is conserved across mammals.

Direct mitochondrial lactate oxidation by LDHB is contested: in isolated rat soleus mitochondria, LDH activity was only ~0.7% of total and lactate alone did not support respiration, cautioning against overcalling mitochondrial LDHB localization/function.