Complex sentence: Choline is first oxidised to betaine aldehyde, a reaction catalysed by the mitochondrial choline oxidase (choline dehydrogenase, EC 1.1.99.1), and betaine aldehyde is further oxidised in the mitochondria or cytoplasm to betaine by betaine aldehyde dehydrogenase (EC 1.1.1.8).
Split into simpler sentences: Choline is first oxidised to betaine aldehyde, a reaction catalysed by the mitochondrial choline oxidase (choline dehydrogenase, EC 1.1.99.1). In a subsequent step, betaine aldehyde is further oxidised in the mitochondria or cytoplasm to betaine by betaine aldehyde dehydrogenase (EC 1.1.1.8).